mysql(1-3)

文章目录

• mysql
• • 1数据库原理
  • • 1.1数据的分类
    • 1.2数据管理发展历史
    • • 1.2.1数据管理的三个阶段
      • 1.2.2文件管理系统的特点
    • 1.3数据库管理系统
    • • 1.3.1相关概念
      • 1.3.2数据库管理系统特点
      • 1.3.3数据库管理系统基本功能
      • 1.3.4数据库管理系统的发展历史
      • **1.3.5数据库软件排名**
    • 1.4关系型数据库理论
    • • [1.4.1 E-R模型](#1.4.1 E-R模型)
      • [1.4.2 联系类型](#1.4.2 联系类型)
      • 1.4.3数据的操作
      • 1.4.4数据库的正规化分析(理论)
      • [1.4.5 SQL结构化查询语言](#1.4.5 SQL结构化查询语言)
  • 2MySQL安装和基本使用
  • • 2.1MySQL介绍
    • • [2.1.1 MySQL **历史**](#2.1.1 MySQL 历史)
      • [2.1.2 MySQL 系列](#2.1.2 MySQL 系列)
      • [2.1.3 MySQL 的特性](#2.1.3 MySQL 的特性)
    • [2.2 MySQL安装](#2.2 MySQL安装)
    • [2.3 MySQL多实例](#2.3 MySQL多实例)
    • • 2.3.1数据库多实例介绍
      • [2.3.2 MySQL多实例配置方案](#2.3.2 MySQL多实例配置方案)
    • 2.4MySQL组成和常用工具
    • • [2.4.1 MySQL主要组成](#2.4.1 MySQL主要组成)
      • [2.4.2 MySQL中的用户账户](#2.4.2 MySQL中的用户账户)
      • [2.4.3 MySQL命令类型](#2.4.3 MySQL命令类型)
      • 2.4.4MySQL客户端使用
      • • 2.4.4.1MySQL客户端常用选项
        • [2.4.4.2 MySQL客户端常用命令](#2.4.4.2 MySQL客户端常用命令)
        • [2.4.4.3 mysqladmin工具](#2.4.4.3 mysqladmin工具)
        • [2.4.4.4 mycli 工具](#2.4.4.4 mycli 工具)
  • [3 SQL语言](#3 SQL语言)
  • • 3.1关系型数据库的构成
    • [3.2 SQL语言介绍](#3.2 SQL语言介绍)
    • • [3.2.1 SQL语言规范](#3.2.1 SQL语言规范)
      • 3.2.2数据库对象和命名
      • [3.2.3 SQL语句分类](#3.2.3 SQL语句分类)
      • [3.2.4 SQL语句构成](#3.2.4 SQL语句构成)
      • 3.2.5字符集和排序
    • 3.3管理数据库
    • • 3.3.1查看数据库列表
      • [3.3.2 创建数据库](#3.3.2 创建数据库)
      • [3.3.3 修改数据库](#3.3.3 修改数据库)
      • [3.3.4 删除数据库](#3.3.4 删除数据库)
    • 3.4数据类型
    • • [3.4.1 数值型](#3.4.1 数值型)
      • [3.4.2 日期和时间型](#3.4.2 日期和时间型)
      • [3.4.3 字符串类型](#3.4.3 字符串类型)
    • [3.5 DDL 语句](#3.5 DDL 语句)
    • • [3.5.1 创建表](#3.5.1 创建表)
      • [3.5.2 查看表](#3.5.2 查看表)
      • [3.5.3 修改和删除表](#3.5.3 修改和删除表)
    • [3.6 DML 语句](#3.6 DML 语句)
    • • [3.6.1 插入数据](#3.6.1 插入数据)
      • [3.6.2 更新数据](#3.6.2 更新数据)
      • [3.6.3 删除数据](#3.6.3 删除数据)
    • [3.7 DQL 语句](#3.7 DQL 语句)
    • • [3.7.1 单表操作](#3.7.1 单表操作)
    • [3.8 MySQL 用户管理](#3.8 MySQL 用户管理)
    • [**3.9 权限管理和DCL语句**](#3.9 权限管理和DCL语句)
    • • [**3.9.1 权限类别**](#3.9.1 权限类别)
      • [**3.9.2 授权**](#3.9.2 授权)
      • [3.9.3 取消权限](#3.9.3 取消权限)
      • [3.9.4 查看用户权限](#3.9.4 查看用户权限)
    • [3.10MySQL 图形化远程管理工具](#3.10MySQL 图形化远程管理工具)
    • • [3.10.1 Navicat 工具](#3.10.1 Navicat 工具)
      • [3.10.2 SQLyog 工具](#3.10.2 SQLyog 工具)
    • [3.11 实现基于LAMP架构的开源网站](#3.11 实现基于LAMP架构的开源网站)
    • • [3.11.1 LAMP 架构说明](#3.11.1 LAMP 架构说明)
      • [3.11.2 PHP 简介](#3.11.2 PHP 简介)
      • [3.11.3 实现博客项目](#3.11.3 实现博客项目)
  • [4. mysql 5.x源码安装](#4. mysql 5.x源码安装)
  • • 基础SQL-DDL语句

mysql

1数据库原理

1.1数据的分类

在数据的获取和使用的过程中，我们可以根据数据的结构类型，将数据分成三类，分别是：结构化数据，半结构化数据，非结构化数据。

结构化数据

结构化数据一般是指可以用二维表来逻辑表达实现的数据。是有固定的格式和有限长度的数据，可以用关系型数据库表示和存储。

其特点是：数据以行为单位，一行数据表示一个实体信息，每一行数据的属性是相同的，存储在数据库中；能够用统一的数据类型和结构加以表示；也能够用二维表结构来逻辑表达实现，包含属性和元组。

对于结构化数据来讲通常是先有结构再有数据。

范例：二维表

no	name	age
1	唐三	123
2	小舞	456

半结构化数据

半结构化数据就是介于完全结构化数据和完全无结构的数据之间的数据。

半结构化数据是结构化数据的一种形式，它并不符合关系型数据库或其它数据表的形式关联起来的数据模型结构，但包含相关的标记，用来分隔语义元素及对记录和字段进行分层，数据的结构和内容混在一起，没有明显的区分，因此，这种数据也被称为自描述结构的数据。

例如：HTML文档，JSON，XML和一些NoSQL数据库等就属于半结构化数据。

对于半结构化数据来说则是先有数据再有结构。

范例：json

[
	{
		"id"：1,
		"name": "唐三",
		"age":123
	},
	{
		"id"：2,
		"name": "叶凡",
		"age":456
	}
]

非结构化数据

顾名思义，就是没有固定结构的数据，这种数据没有固定格式和有限长度，无法用数据库二维逻辑表来表现其结构，对于这类数据，我们一般进行整体存储。

典型的非结构化数据包括：二进制文件，音视频文件，位置信息等

1.2数据管理发展历史

如何有效管理大量数据，方法和手段都在随着计算机技术的发展而进步。

数据管理的发展经历了人工管理、文件系统和数据库系统三个发展阶段。

1.2.1数据管理的三个阶段

人工管理阶段

时间：20世纪50年代中期以前

特点：当时的计算机主要用于科学计算。外部存储设备只有磁带，打孔纸带等，也没有专业的数据管理

软件，所以在当时数据管理主要由人工完成。数据处理方式上基本是批处理。

文件系统管理阶段

时间：20世纪50年代后期至60年代中期

特点：随着时间的发展，计算机不仅用于科学计算，还用于信息管理，需要处理的数据量大增，数据存储，检索和维护等问题迫切需要解决，同一时期，在硬件方面，出现了磁盘，磁鼓等可以直接连机存取的设备，在此基础上，出现了基于文件系统的数据管理软件。使用磁盘文件的形式来管理数据，数据可以在系统中长期保存，文件也有了各种各样的格式。在数据处理方式上可以批处理，也可以联机实时处理。

数据库系统阶段

时间：20世纪60年代后期至今

特点：此时己经出现大容量的磁盘，且硬件价格开始下降。数据管理技术进入数据库系统阶段。数据库系统克服了文件系统的缺陷，提供了对数据更高级、更有效的管理。这个阶段的程序和数据的联系是通过数据库管理系统来实现的。数据库系统采用了复杂的结构化的数据模型，数据拥有高独立性，低冗余度。

1.2.2文件管理系统的特点

优点

文件形式和格式多样化，数据可以长期保存，且数据具有一定的独立性，由文件系统进行管理。

缺点

应用程序对接不方便，没有统一接口，也不支持对文件的并发访问，无安全控制功能，难以按用户视图表示数据，数据间联系弱，数据冗余不可避免。

1.3数据库管理系统

1.3.1相关概念

数据库：Database

数据库是按照一定的数据结构来组织，存储和管理数据的仓库。

是一个长期存储在计算机内的、有组织的、可共享的、统一管理的大量数据的集合。

数据库管理系统：Database Management System(DBMS)

数据库管理系统是一种操纵和管理数据库的大型软件，用于建立，使用和维护数据库，简称DBMS。

它对数据库进行统一的管理和控制，以保证数据库的安全性和完整性。

数据库管理员：Database Administrator(DBA)

DBA是从事管理和维护数据库管理系统（DBMS）的相关工作人员的统称，属于运维工程师的一个分支，主要负责业务数据库从设计、测试到部署交付的全生命周期管理。

DBA的核心目标是保证数据库管理系统的稳定性、安全性、完整性和高可用性能。

应用程序：Application

一个应用程序通常是指能够执行某种功能的软件程序。

1.3.2数据库管理系统特点

• 数据库管理系统中采用了复杂的数据模型表示数据结构，数据冗余小，易扩充，实现了数据共享。

• 具有较高的数据和程序独立性。数据库的独立性表现在物理独立性和逻辑独立性两个方面。

• 数据库管理系统为用户和应用程序提供了方便和统一的查询接口。

• 数据库管理系统的存在，使得数据可以和应用程序解耦。

• 数据库管理系统还具有并发控制，数据备份和恢复，完整性和安全性保障等功能。

1.3.3数据库管理系统基本功能

1. 数据的定义：DBMS提供了数据定义语言DDL（DataDefinition Language），供用户定义数据库的三级模式结构，两级映像以及完整性约束和保密限制等约束。DDL主要用于建立、修改数据库的库结构。DDL所描述的库结构仅仅给出了数据库的框架，数据库的框架信息被存放在数据字典中。

2. 数据操作：DBMS提供数据操作语言DML（DataManipulation Language），供用户实现对数据的追加、删除、更新、查询等操作。

3. 数据组织、存储与管理：DBMS要分类组织、存储和管理各种数据，包括数据字典、用户数据、存取路径等，需确定以何种文件结构和存取方式在存储级上组织这些数据，如何实现数据之间的联系。数据组织和存储的基本目标是提高存储空间利用率，选择合适的存取方法提高存取效率。

4. 数据库的运行管理：数据库的运行管理功能是DBMS的运行控制、管理功能，包括多用户环境下的并发控制、安全性检查和存取限制控制、完整性检查和执行、运行日志的组织管理、事务的管理和自动恢复，即保证事务的原子性。这些功能保证了数据库系统的正常运行。

5. 数据库的维护：这一部分包括数据库的数据载入、转换、转储、数据库的重组和重构以及性能监控等功能，这些功能分别由各个使用程序来完成。

6. 数据库的保护：数据库中的数据是信息社会的战略资源，所以数据的保护至关重要。DBMS对数据库的保护通过4个方面来实现：数据库的恢复、数据库的并发控制、数据库的完整性控制、数据库安全性控制。DBMS的其他保护功能还有系统缓冲区的管理以及数据存储的某些自适应调节机制等。

7. 通信：DBMS具有与操作系统的联机处理、分时系统及远程作业输入的相关接口，负责处理数据的传送。对网络环境下的数据库系统，还应该包括DBMS与网络中其他软件系统的通信功能以及数据库之间的互操作功能。

1.3.4数据库管理系统的发展历史

自20世纪60年代中后期开始，使用电脑进行数据处理的规模越来越大，同时也出现了大容量的磁盘存储设备，操作系统也日渐成熟，为了解决数据的独立性问题，实现数据的统一管理，达到数据共享的目的，出现了数据库技术。

数据库技术从出现至今，经历了多次的迭代行进，在这个过程中，按时间和特性，可以将数据库管理系统分为三类。

层次数据库

层次模型数据库系统是最早研制成功的数据库系统，这种数据库中的数据被组织成一个树状模型，这种结构简单，但缺乏灵活性，各数据之间仅限于一对多的关系。

这种数据库最成功的典型代表是IBM的IMS（信息管理系统）。

网状数据库

网状数据库是采用网状原理和方法，以网状数据模型为基础建立的数据库。

网状数据模型是以记录类型为结点的网络结构，即一个结点可以有一个或多个下级结点，也可以有一个或多个上级结点，两个结点之间甚至可以有多种联系，两个记录类型之间的值可以是多对多的联系。

关系型数据库管理系统

关系数据库管理系统：Relational DatabaseManagement System(RDBMS)是指包括相互联系的逻辑组织和存取这些数据的一套程序（数据库管理系统软件）。关系数据库管理系统就是管理关系数据库，并将数据逻辑组织的系统。

常见的关系型数据库管理系统有Oracle，MySQL，DB2，SQLServer等。

关系型数据库，是指采用了关系模型来组织数据的数据库，其以行和列的形式存储数据，以便于用户理解，关系型数据库这一系列的行和列被称为表，一组表组成了数据库。用户通过查询来检索数据库中的数据，而查询是一个用于限定数据库中某些区域的执行代码。关系模型可以简单理解为二维表格模型，而一个关系型数据库就是由二维表及其之间的关系组成的一个数据组织。

关系型数据库中的相关概念

在我们开始学习MySQL 数据库前，让我们先了解下RDBMS的一些术语：

• 数据库: 数据库是一些关联表的集合。

• 数据表: 表是数据的矩阵。在一个数据库中的表看起来像一个简单的电子表格。

• 列(column): 一列(数据元素) 包含了相同类型的数据, 例如邮政编码的数据。

• **行(Row)：**一行（元组，或记录）是一组相关的数据，例如一条用户订阅的数据。

• 冗余：存储两倍数据，冗余降低了性能，但提高了数据的安全性。

• 主键(Primary key)：主键是唯一的。一个数据表中只能包含一个主键。你可以使用主键来查询数据。

• **外键：**外键用于关联两个表。

• 复合键：复合键（组合键）将多个列作为一个索引键，一般用于复合索引。

• **索引：**使用索引可快速访问数据库表中的特定信息。索引是对数据库表中一列或多列的值进行排序的一种结构。类似于书籍的目录。

• 参照完整性: 参照的完整性要求关系中不允许引用不存在的实体。与实体完整性是关系模型必须满足的完整性约束条件，目的是保证数据的一致性。

MySQL 为关系型数据库(Relational Database Management System), 这种所谓的"关系型"可以理解为"表格"的概念, 一个关系型数据库由一个或数个表格组成, 如图所示的一个表格:

• 表头(header): 每一列的名称;

• 列(col): 具有相同数据类型的数据的集合;

• 行(row): 每一行用来描述某条记录的具体信息;

• 值(value): 行的具体信息, 每个值必须与该列的数据类型相同;

• 键(key): 键的值在当前列中具有唯一性。

常见的关系型数据库系统

MySQL：MySQL,MariaDB,Percona Server

PostgreSQL：PgSQL,EnterpriseDB

Oracle：Oracle

SQLServer：MS SQLServer

DB2

1.3.5数据库软件排名

https://db-engines.com/en/ranking

1.4关系型数据库理论

1.4.1 E-R模型

ER模型，全称为实体联系模型、实体关系模型或实体联系模式图（ERD：Entity-relationship model），它提供不受任何DBMS约束的面向用户的表达方法，在数据库设计中被广泛用作数据建模的工具。

E-R图模型的组成是由实体，属性和联系三部份组成。

实体：（Entity）实体是数据的使用者，代表软件系统中客观存在的生活中的实物，同一类实体构成实体集。在ER图中，实体用矩形表示。

属性：（Attribute）实体中的所有特性称为属性，每个属性描述的是实体的单个特性。在ER图中，属性用椭圆形表示。

联系：（Relationship）描述了实体的属性之间的关联规则。在ER图中，联系用菱形表示。ER模型范

例：

1.4.2 联系类型

实体间的联系有三种类型：

一对一联系（1:1）：例如，一个学号只能分配给一个同学，每个同学都有一个学号，则学号与同学的联系是一对一。

一对多联系（1:n）：例如，一个老师可以教授多门课程，每门课程只能有一个老师教授，则老师与课程的联系是一对多。

多对多联系（m:n）：例如，一个同学可以报名多门课程，每门课程下有多个同学，则同学与课程的联系是多对多。

学生表一对---

stu_id	name
1	唐三
2	小舞

老师表一对---

teacher_id	name
1	gao
2	ma

老师与课程一对多

class_id	name	teacher_id
1	linux	1
2	golang	1
3	python	2
4	java	2

学生与课程多对多

class_id	stu_id
1	1
1	2
2	1
2	2
3	1
3	2

1.4.3数据的操作

数据库中对数据的操作主要包括增删改查

操作描述	作用	SQL关键字
Create	增加数据	Insert
Read	读取数据	Select
Update	更新数据	Update
Delete	删除数据	Delete

1.4.4数据库的正规化分析(理论)

数据库规范化，又称数据库或资料库的正规化、标准化，是数据库设计中的一系列原理和技术，以减少数据库中数据冗余，增进数据的一致性。设计关系数据库时，遵从不同的规范要求，设计出合理的关系型数据库，不同的规范要求被称为不同范式，各种范式呈递次规范，越高的范式数据库冗余越小。

目前关系数据库有六种范式：第一范式（1NF）、第二范式（2NF）、第三范式（3NF）、巴德斯科范式（BCNF）、第四范式(4NF）和第五范式（5NF，又称完美范式）。满足最低要求的范式是第一范式（1NF）。在第一范式的基础上进一步满足更多规范要求的称为第二范式（2NF），其余范式以次类推。一般数据库只需满足第三范式（3NF）即可。

第一范式1NF（确保每列保持原子性）

第一范式是最基本的范式。如果数据库表中的所有字段值都是不可分解的原子值，就说明该数据库表满足了第一范式。

第一范式需要根据系统的实际需求来定。其核心是要保证数据表中的列里面没有重复值，即实体中的某个属性不能有多个值或者不能有重复的属性，确保每一列的原子性。

列重复

id	teacher_name	class_1	class_2	class_3
1	ma	golang	linux	python
2	gao	golang	linux
3	ma	golang

列不重复

id	teacher_name	class
1	ma	golang
2	ma	linux
3	ma	python
4	gao	golang
5	gao	linux
6	ma	golang

第二范式2NF（确保表中的每列都和主键相关）

第二范式在第一范式的基础之上更进一层。第二范式需要确保数据库表中的每一列都和主键相关，而不能只与主键的某一部分相关（主要针对联合主键而言）。也就是说在一个数据库表中，一个表中只能保存一种数据，不可以把多种数据保存在同一张数据库表中。

teacher_name 和city组成联合主键，city_code与city------对应，city_code依赖了部份主键，违反了第二范式

teacher_name	city	age	city_code
gao	bj	30	010
ma	bj	32	010
deng	bj	21	021

teacher_name与ctiy_id组成联合主键，再用city_id关联city_name和city_code，这样符合第二范式

第三范式3NF（确保每列都和主键列直接相关，而不是间接相关）

第三范式需要确保数据表中的每一列数据都和主键直接相关，而不能间接相关。

必须先满足第一范式才能满足第二范式，必须同时满足第一第二范式才能满足第三范式。

1.4.5 SQL结构化查询语言

SQL:（StructureQueryLanguage），结构化查询语言。是一种数据库查询和程序设计语言，用于存取数据以及查询、更新和管理关系数据库系统，SQL语句就是用SQL语言写的用于操作数据库的语句。

关系型数据库一般工作于C/S模式下，使用专有协议进行通信，服务端程序监听特有端口，客户端程序发送查询语句到服务端，服务端将查询结果返回给客户端。

MySQL自带CLI接口，GUI接口可以使用第三方工具实现，在应用程序或后端开发语言中，使用相应的编程语言下的数据库驱动来进行与数据库服务端的通信。

2MySQL安装和基本使用

2.1MySQL介绍

2.1.1 MySQL 历史

MySQL 之父

关于 MariaDB、MySQL、MaxDB 名字的由来，这里有个不得不说的小插曲。Monty 有一个女儿，名叫 My，因此他将自己开发的数据库命名为 MySQL。Monty 还有一个儿子，名为 Max，因此在 2003 年，SAP 公司与 MySQL 公司建立合作伙伴关系后，Monty 又将与 SAP 合作开发的数据库命名为 MaxDB。而现在的 MariaDB 中的 Maria 是 Monty 小孙女(小女儿？)的名字。

Michael "Monty" Widenius, 1962 年 3 月 3 日出生于芬兰赫尔辛基。

开源 MySQL 数据库的创始成员、MySQL AB 公司的首席技术官、MySQL 数据库第一行代码的作者、MySQL 数据库命名人、MariaDB 创始人兼首席技术官；独自完成撰写 MySQL 数据库服务器端 95% 的代码。

MySQL历史

MySQL 的海豚标志的名字叫 "sakila"，它是由 MySQL AB 的创始人从用户在 "海豚命名" 的竞赛中建议的大量的名字表中选出的。获胜的名字是由来自非洲斯威士兰的开源软件开发者 Ambrose Twebaze 提供。根据 Ambrose 所说，Sakila 来自一种叫 SiSwati 的斯威士兰方言，也是在Ambrose 的家乡乌干达附近的坦桑尼亚的 Arusha 的一个小镇的名字

MySQL 的历史可以追溯到 1979 年。当时 Allan Larsson 和 Michael Widenius (Monty) 开了一家自己的咨询公司，取名 TcX，名字的由来已无从考证。有道是" 前世尽付真情，今生亦现福缘积厚"。那年一个夜黑风高的晚上，Michael 基于 BASIC 语言写出了他的第一款数据库报表工具 UNIREG。

有当年的天气记录为证，Michael 写完该工具时极光异常明亮，炫彩无比。大凡重大事情的发生，后来的著述人都会记录有一些类似的怪现象。比如刮风、下雨、冒仙气什么的，还有天上星星异常闪烁等等，反正就是说明这种事情很不简单。

最初的 UNIREG 是运行在瑞典人制造的 ABC800 计算机上的。ABC800 的内存只有 32KB，CPU 是频率只有 4MHz 的 Z80。在 1983 年 Monty 遇到了 David Axmark，两人相见恨晚，开始合作运营 TcX，Monty 负责技术，David 搞管理。后来 TcX 将 UNIREG 移植到其他更加强大的硬件平台，主要是 Sun 的平台。

一次 Monty 接到了一个项目，需要为当时的 UNIREG 提供更加通用的 SQL 接口，Monty 找到了 David Hughes --mSQL 的发明人，商讨合作事宜。然而，经过一番测试后，他们发现 mSQL 的速度并不尽如人意，无法满足客户的需求。

遇到这种问题，程序员出身的 Monty 无法委曲求全，毅然采取了革命性的态度--重新设计整个系统。1995 年 5 月 23 日，MySQL 的第一个内部版本发行了，并在第二年对外公布了 MySQL 官方正式发行版(3.11.1)。有趣的是，第一个 MySQL 正式版恰巧只能运行在 Sun Solaris 上，仿佛昭示了它日后被 Sun收购的命运。

在接下来的两年中，MySQL 被移植到不同的平台，同时加入了不少新的特性。到 1998 时，MySQL 能够运行在 10 多种操作系统之上，其中包括应用非常广泛的 FreeBSD、Linux、Windows 95 和 Windows NT 等。很快 MySQL 3.22 也发布了，但它仍然存在很多问题--如不支持事务操作、子查询、外键、存储过程和视图等功能。正因为这些缺陷，当时许多 Oracle 和 SQL Server 的用户对 MySQL 根本不屑一顾。

大概在 1999 的冬天，下了很大一场雪。然后独立的商业公司 MySQL AB 就在瑞典的中部城市 Uppsala成立了。并于同年发布了包含事务型存储引擎 BDB 的 MySQL 3.23。在集成 BDB 存储引擎的过程中，MySQL 开发团队得到了很好的锻炼，为后来能将 InnoDB 整合以及开发开放插件式的存储引擎架构打下了坚实的基础。

MySQL 从诞生之初就提供了双重的授权标准：个人使用是免费的，如果用于商业网站搭建或者Windows 平台下就必须购买商业许可证。在 2000 年的时候 MySQL 做了一个重大的决定，改换成了GPL 许可模式，也就是说商业用户也无需再购买许可证，但必须把他们的源码公开。虽然 MySQL AB 因此在收入上遭受了巨大的打击，损失了将近 80% 的收入，但他们依然坚持了 GPL 许可模式。

与此同时，芬兰公司 Heikki 开始接触 MySQL AB，讨论将 Heikki 的存储引擎 InnoDB 整合到 MySQL 数据库中的可行性。双方的合作非常顺利，并于 2001 年推出 MySQL 4.0 Alpha 版本。经过两年的公开测试和应用，到了 2003 年，包含 InnoDB 的 MySQL 已经变得非常稳定了。随即在同一年，MySQL 推出4.1 版，第一次使得 MySQL 支持子查询，支持 Unicode 和预编译 SQL 等功能。

MySQL 4.1 还在 Alpha 版时，公司已决定并行开发 5.0 版。因为他们打算加快 MySQL 的开发速度以适应日益苛刻的市场需求。这个新版本是有史以来 MySQL 最大的变化，添加了存储过程、服务端游标、触发器、查询优化以及分布式事务等在大家看来一个" 正常数据库管理系统" 应当拥有的一整套功能。

2008 年 2 月，当时的业界开源老大 Sun Microsystems 动用 10 亿美元收购了 MySQL，造就了开源软件的收购最高价。这次交易给开源交易设立了一个新的基准。在此之前的交易金额 (JBoss、Zimbra、XenSource、Gluecode) 从没接近过 10 亿美元，全部加起来才差不多与 Sun Microsystems 购买MySQL 的花费持平。MySQL 被收购之后，MySQL 图标停止使用，取而代之的是 Sun/MySQL 图标。

MySQL 和 Sun 合并之后，推出了 MySQL 5.1GA 版和 MySQL 5.4 Beta 版。5.4 的推出照搬了 4.1 和 5.0当时的开发模式，让 5.4 和 6.0 并行处于 Beta 开发阶段。

螳螂捕蝉，黄雀在后。2009 年，数据库老大 Oracle 大笔一挥，开出 74 亿美元的支票，将 Sun Microsystems 和 MySQL 通盘收于旗下。

这里附带说明一下 Drizzle，它是 Sun/MySQL 的 Brian 在 2008 年提出的一个计划。目标是将开发一个更小、更轻、更快的数据库，用作云计算 (Cloud Computing) 和 Web 应用的基础架构。

标志性事件

1999 年，MySQL AB 在瑞典正式宣布成立。

2000 年，ISAM 华丽转身 MyISAM 存储引擎。同年 MySQL 开放了自己的源代码，并且基于 GPL 许可协议。同年 9 月 innoDB 推出。

2003 年，MySQL4.0 发布，正式集成 innodb

2005 年，MySQL 5.0 发布。同年 Oracle 把 InnoDB 引擎的开发公司 innobase 收购完成。MySQL 明确地表现出迈向高性能数据库的发展步伐。

2006 年，sun 公司收购了 MySQL 公司，出价 10 亿美元。

2009 年，Oracle 公司收购 sun，将 MySQL 纳入囊中。

2010 年，MySQL 5.5 正式版发布，Oracle 完成了大量改进，并将 innodb 改成默认引擎。

2013 年，MySQL 5.6 GA 版本发布。

近期 - MySQL 5.7 GA 版本横空出世，其性能、新特性、性能分析带来了质的改变。

全球最大网站Top20,90%在使用Mysql

• Facebook.com

• Google.com

• YouTube.com

• Yahoo.com

• WIKipedia.org - 维基百科

• Live.com -- 微软新的电子邮件服务

• qq.com -- 腾讯

• Microsoft.com -- 微软产品 / 更新 / 下载

• Baidu.com -- 百度

• Msn.com -- 微软自有互联网信息

• Blogger.com -- 博客平台

• ASK.com - 搜索引擎

• Taobao.com 淘宝

• Twiter.com -- 实时通讯平台

• Bing.com -- 必应

• Sohu.com -- 搜狐

• Apple.com -- 苹果

• WrodPress.com -- 成行经历

• Sina.com -- 新浪

• Amazon.com - 亚马逊

2.1.2 MySQL 系列

尽管 MySQL 是最受欢迎的程序之一，但是许多开发人员认为有必要将其拆分成其他项目，并且每个分支项目都有自己的专长。该需求以及 Oracle 对核心产品增长缓慢的担忧，导致出现了许多开发人员感兴趣的子项目和分支。本文将讨论受人们关注的三个流行 MySQL 分支：Drizzle、MariaDB 和 Percona Server（包括 XtraDB 引擎）

MySQL

官方 MySQL，前身 MySQL AB / SUM / 最后被 Oracle 公司收入麾下。

Percona

Percona Server 就是这样一款产品，由领先的 MySQL 咨询公司 Percona 发布。Percona Server 是一款独立的数据库产品，为用户提供了换出其 MySQL 安装并换入 Percona Server 产品的能力。通过这样做，就可以利用 XtraDB 存储引擎。Percona Server 声称可以完全与 MySQL 兼容，因此从理论上讲，您无需更改软件中的任何代码。这确实是一个很大的优势，适合在您寻找快速性能改进时控制质量。因此，采用 Percona Server 的一个很好的理由是，利用 XtraDB 引擎来尽可能地减少代码更改。

此外，他们是 XtraDB 存储引擎的原作者。Percona 将此代码用作开源代码，因此您可以在其他产品中找到它，但引擎的最初创建者与编写此产品的是同一个人，所以您可以随心所欲地使用此信息。

Percona 团队的最终声明是 "Percona Server 是由 Oracle 发布的最接近官方 MySQL Enterprise 发行版的版本"，因此与其他更改了大量基本核心 MySQL 代码的分支有所区别。Percona Server 的一个缺点是他们自己管理代码，不接受外部开发人员的贡献，以这种方式确保他们对产品中所包含功能的控制。

下面是 Percona Server 的声明，该声明来自它们自己的网站：

• 可扩展性：处理更多事务；在强大的服务器上进行扩展

• 性能：使用了 XtraDB 的 Percona Server 速度非常快

• 可靠性：避免损坏，提供崩溃安全 (crash-safe) 复制

• 管理：在线备份，在线表格导入 / 导出

• 诊断：高级分析和检测

• 灵活性：可变的页面大小，改进的缓冲池管理

MariaDB

MySQL 之父 Widenius 先生离开了 Sun 之后，觉得依靠 Sun/Oracle 来发 展 MySQL，实在很不靠谱，

是决定另开分支，这个分支的名字叫做 MariaDB；

在卖出 MySQL 之后 Widenius 发现两个主要问题：

• MySQL 核心开发团队是封闭的，完全没有 Oracle 之外的成员参加。很多高手即使 有心做贡献，也没办法做到

• MySQL 新版本的发布速度，在 Oracle 收购 Sun 之后大为减缓。Widenius 用数据比 较了收购之前和之后新版本的发布速度。有很多 bugfix 和新的 feature，都没有及 时加入到发布版本之中

目标是提供一个由社区开发的、稳定的、总是免费的 MySQL 分支，在用 户级别上兼容主流版本。我们为自己的版本和上游、社区版的互操作性 提高而努力；Monty Program 公司承诺 MariaDB 将会一直保持独立和开源。值得一提的是，Fedora 及 OpenSUSE Linux 更宣布将在 MariaDB 推出下 一个版本后抛弃 MySQL 使用 MariaDB。

MariaDB 提供了 MySQL 提供的标准存储引擎，即 MyISAM 和 InnoDB。因此，实际上，可以将它视为MySQL 的扩展集，它不仅提供 MySQL 提供的所有功能，还提供其他功能。MariaDB 还声称自己是MySQL 的替代，因此从 MySQL 切换到 MariaDB 时，无需更改任何基本代码即可安装它。

最后可能也是最重要的一点是，MariaDB 的主要创建者是 Monty Widenius，也是 MySQL 的初始创建者。Monty 成立了一家名为 Monty Program 的公司来管理 MariaDB 的开发，这家公司雇佣开发人员来编写和改进 MariaDB 产品。这既是一件好事，也是一件坏事：有利的一面在于他们是 Maria 功能和 bug修复的佼佼者，但公司不是以赢利为目的，而是由产品驱动的，这可能会带来问题，因为没有赢利的公司不一定能长久维持下去。

2.1.3 MySQL 的特性

• MySQL是基于开源协议发布的，可以免费使用，也可以基于源码进行二次开发。

• MySQL使用标准SQL语言进行管理。

• MySQL可以运行于多个系统上，具有跨平台特性，并且支持多种语言。

• MySQL使用插件式存储引擎，不同的存储引擎，有着不同的功能和特性，使用者可以根据需要灵活选择。

• MySQL基于单进程，多线程的模式进行工作。

• MySQL提供了大量的测试组件和诸多的扩展

2.2 MySQL安装

参考 mysql安装 手册

2.3 MySQL多实例

2.3.1数据库多实例介绍

什么是数据库多实例

拿MySQL数据库来说明，就是在一台服务器上运行多个MySQL服务端进程，每个进程监听一个端口（3306，3307，3308），维护一套属于其自己的配置和数据，客户端使用不同的端口来连接具体服端进程，从而实现对不同的实例的操作。

多实例的优点

• 节约硬件资源：在某些场景下（比如说测试，调研，新I旧业务并存等），需要配置不同的MySQL数据库版本，而又没有足够多的服务器资源，则可以选择在一台服务器上用不同的版本实现多开来满足需求。

• 便于对比：在一个完全相同的硬件环境中，运行不同的MySQL版本，使用相同的参数进行测试，调研时，可以最大程度的减少外部环境因素的影响，便于得出更准确的结论。

• 便于管理：在一台服务器上运行多个实例，同理，只需要在这一台服务器上配置安全规则，就可以完成对多个实例的访问授权，而且对于数据库的备份，停启等工作，也只需要在这一台服务器上完成。

多实例的缺点

• 资源抢占：一台服务器上运行多个服务实例，资源总量恒定，一个实例占用的资源无法被另一个实例所使用，在这种情况下，服务性能会受到影响，无法体现MySQL服务的实际性能。

• 存在单点风险：一台服务器上部署多个服务实例，如果该服务器当机，则这多个服务实例都会受影响。

2.3.2 MySQL多实例配置方案

可以用不同的MySQL版本实现多实例，也可以用相同的MySQL版本实现多实例。

2.4MySQL组成和常用工具

2.4.1 MySQL主要组成

mysql基于C/S模式提供服务，主要有客户端程序和服务端程序组成，另外还有一些管理工具。

服务端主要组成

程序	功能
mysqld_safe	安全启动脚本
mysqld	服务端程序，是mysql服务的核心程序
mysqld_multi	多实例工具

客户端主要组成

程序	功能
mysql	基于mysql协议的交互式CLI工具
mysqldump	备份工具
mysqladmin	服务端管理工具
mysqlimport	数据导入工具

MyISAM存储引擎的管理工具

程序	功能
myisamchk	检测MyISAM
myisampack	打包MyISAM表，只读

配置文件

不同版本配置文件略有不同

[root@localhost ~ 09:43:36]# cat /etc/my.cnf
#
# This group is read both both by the client and the server
# use it for options that affect everything
#
[client-server]

#
# include all files from the config directory
#
!includedir /etc/my.cnf.d

[root@localhost ~ 09:44:05]# tree /etc/my.cnf.d/
/etc/my.cnf.d/
├── client.cnf   #客户端配置
├── mysql-default-authentication-plugin.cnf
└── mysql-server.cnf  #服务器端配置

0 directories, 3 files

生效顺序

[root@localhost ~ 09:44:16]# mysql --help |grep my.cnf
                      order of preference, my.cnf, $MYSQL_TCP_PORT,
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf

2.4.2 MySQL中的用户账户

详见MySQL用户管理

2.4.3 MySQL命令类型

MySQL中的命令分为两类，分别是客户端命令和服务端命令。

客户端命令在本地执行。服务端命令发送到服务端执行，再返回执行结果到客户端上。

客户端命令和服务端命令，都是通过MySQL客户端工具进行输入输出。

查看所有客户端命令

[root@localhost ~ 09:44:38]# mysql -uroot -p123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> ?

For information about MySQL products and services, visit:
   http://www.mysql.com/
For developer information, including the MySQL Reference Manual, visit:
   http://dev.mysql.com/
To buy MySQL Enterprise support, training, or other products, visit:
   https://shop.mysql.com/

List of all MySQL commands:
Note that all text commands must be first on line and end with ';'
?         (\?) Synonym for `help'.
clear     (\c) Clear the current input statement.
connect   (\r) Reconnect to the server. Optional arguments are db and host.
delimiter (\d) Set statement delimiter.
edit      (\e) Edit command with $EDITOR.
ego       (\G) Send command to mysql server, display result vertically.
exit      (\q) Exit mysql. Same as quit.
go        (\g) Send command to mysql server.
help      (\h) Display this help.
nopager   (\n) Disable pager, print to stdout.
notee     (\t) Don't write into outfile.
pager     (\P) Set PAGER [to_pager]. Print the query results via PAGER.
print     (\p) Print current command.
prompt    (\R) Change your mysql prompt.
quit      (\q) Quit mysql.
rehash    (\#) Rebuild completion hash.
source    (\.) Execute an SQL script file. Takes a file name as an argument.
status    (\s) Get status information from the server.
system    (\!) Execute a system shell command.
tee       (\T) Set outfile [to_outfile]. Append everything into given outfile.
use       (\u) Use another database. Takes database name as argument.
charset   (\C) Switch to another charset. Might be needed for processing binlog with multi-byte charsets.
warnings  (\W) Show warnings after every statement.
nowarning (\w) Don't show warnings after every statement.
resetconnection(\x) Clean session context.
query_attributes Sets string parameters (name1 value1 name2 value2 ...) for the next query to pick up.

For server side help, type 'help contents'

查看所有服务端命令

mysql> help contents
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Account Management
   Administration
   Components
   Compound Statements
   Contents
   Data Definition
   Data Manipulation
   Data Types
   Functions
   Geographic Features
   Help Metadata
   Language Structure
   Loadable Functions
   Plugins
   Prepared Statements
   Replication Statements
   Storage Engines
   Table Maintenance
   Transactions
   Utility

查看服务端命令具体项

mysql> help administration
You asked for help about help category: "Administration"
For more information, type 'help <item>', where <item> is one of the following
topics:
   BINLOG
   CACHE INDEX
   FLUSH
   HELP COMMAND
   KILL
   LOAD INDEX
   RESET
   RESET PERSIST
   RESTART
   SET
   SET CHARACTER SET
   SET CHARSET
   SET NAMES
   SHOW
   SHOW BINARY LOGS
   SHOW BINLOG EVENTS
   SHOW CHARACTER SET
   SHOW COLLATION
   SHOW COLUMNS
   SHOW CREATE DATABASE
   SHOW CREATE EVENT
   SHOW CREATE FUNCTION
   SHOW CREATE PROCEDURE
   SHOW CREATE SCHEMA
   SHOW CREATE TABLE
   SHOW CREATE TRIGGER
   SHOW CREATE USER
   SHOW CREATE VIEW
   SHOW DATABASES
   SHOW ENGINE
   SHOW ENGINES
   SHOW ERRORS
   SHOW EVENTS
   SHOW FIELDS
   SHOW FUNCTION CODE
   SHOW FUNCTION STATUS
   SHOW GRANTS
   SHOW INDEX
   SHOW MASTER LOGS
   SHOW MASTER STATUS
   SHOW OPEN TABLES
   SHOW PLUGINS
   SHOW PRIVILEGES
   SHOW PROCEDURE CODE
   SHOW PROCEDURE STATUS
   SHOW PROCESSLIST
   SHOW PROFILE
   SHOW PROFILES
   SHOW RELAYLOG EVENTS
   SHOW REPLICA STATUS
   SHOW REPLICAS
   SHOW SCHEMAS
   SHOW SLAVE HOSTS
   SHOW SLAVE STATUS
   SHOW STATUS
   SHOW TABLE STATUS
   SHOW TABLES
   SHOW TRIGGERS
   SHOW VARIABLES
   SHOW WARNINGS
   SHUTDOWN

查看详细帮助

mysql> help binlog
Name: 'BINLOG'
Description:
Syntax:
BINLOG 'str'

BINLOG is an internal-use statement. It is generated by the mysqlbinlog
program as the printable representation of certain events in binary log
files. (See https://dev.mysql.com/doc/refman/8.0/en/mysqlbinlog.html.)
The 'str' value is a base 64-encoded string the that server decodes to
determine the data change indicated by the corresponding event.

To execute BINLOG statements when applying mysqlbinlog output, a user
account requires the BINLOG_ADMIN privilege (or the deprecated SUPER
privilege), or the REPLICATION_APPLIER privilege plus the appropriate
privileges to execute each log event.

URL: https://dev.mysql.com/doc/refman/8.0/en/binlog.html

2.4.4MySQL客户端使用

MySQL服务基于C/S架构，用户主要使用客户端工具来与远程服务端进行连接，从而与MySQL服务进行交互。

2.4.4.1MySQL客户端常用选项

格式：

[root@localhost ~ 10:01:57]# mysql --help
mysql  Ver 8.0.26 for Linux on x86_64 (Source distribution)
Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Usage: mysql [OPTIONS] [database]
  -?, --help          Display this help and exit.
  -I, --help          Synonym for -?
  --auto-rehash       Enable automatic rehashing. One doesn't need to use
                      'rehash' to get table and field completion, but startup
                      and reconnecting may take a longer time. Disable with
                      --disable-auto-rehash.
                      (Defaults to on; use --skip-auto-rehash to disable.)
  -A, --no-auto-rehash
                      No automatic rehashing. One has to use 'rehash' to get
                      table and field completion. This gives a quicker start of
                      mysql and disables rehashing on reconnect.
  --auto-vertical-output
                      Automatically switch to vertical output mode if the
                      result is wider than the terminal width.
  -B, --batch         Don't use history file. Disable interactive behavior.
                      (Enables --silent.)
  --bind-address=name IP address to bind to.
  --binary-as-hex     Print binary data as hex. Enabled by default for
                      interactive terminals.
  --character-sets-dir=name
                      Directory for character set files.
  --column-type-info  Display column type information.
  -c, --comments      Preserve comments. Send comments to the server. The
                      default is --skip-comments (discard comments), enable
                      with --comments.
  -C, --compress      Use compression in server/client protocol.
  -#, --debug[=#]     This is a non-debug version. Catch this and exit.
  --debug-check       This is a non-debug version. Catch this and exit.
  -T, --debug-info    This is a non-debug version. Catch this and exit.
  -D, --database=name Database to use.
  --default-character-set=name
                      Set the default character set.
  --delimiter=name    Delimiter to be used.
  --enable-cleartext-plugin
                      Enable/disable the clear text authentication plugin.
  -e, --execute=name  Execute command and quit. (Disables --force and history
                      file.)
  -E, --vertical      Print the output of a query (rows) vertically.
  -f, --force         Continue even if we get an SQL error.
  --histignore=name   A colon-separated list of patterns to keep statements
                      from getting logged into syslog and mysql history.
  -G, --named-commands
                      Enable named commands. Named commands mean this program's
                      internal commands; see mysql> help . When enabled, the
                      named commands can be used from any line of the query,
                      otherwise only from the first line, before an enter.
                      Disable with --disable-named-commands. This option is
                      disabled by default.
  -i, --ignore-spaces Ignore space after function names.
  --init-command=name SQL Command to execute when connecting to MySQL server.
                      Will automatically be re-executed when reconnecting.
  --local-infile      Enable/disable LOAD DATA LOCAL INFILE.
  -b, --no-beep       Turn off beep on error.
  -h, --host=name     Connect to host.
  --dns-srv-name=name Connect to a DNS SRV resource
  -H, --html          Produce HTML output.
  -X, --xml           Produce XML output.
  --line-numbers      Write line numbers for errors.
                      (Defaults to on; use --skip-line-numbers to disable.)
  -L, --skip-line-numbers
                      Don't write line number for errors.
  -n, --unbuffered    Flush buffer after each query.
  --column-names      Write column names in results.
                      (Defaults to on; use --skip-column-names to disable.)
  -N, --skip-column-names
                      Don't write column names in results.
  --sigint-ignore     Ignore SIGINT (CTRL-C).
  -o, --one-database  Ignore statements except those that occur while the
                      default database is the one named at the command line.
  --pager[=name]      Pager to use to display results. If you don't supply an
                      option, the default pager is taken from your ENV variable
                      PAGER. Valid pagers are less, more, cat [> filename],
                      etc. See interactive help (\h) also. This option does not
                      work in batch mode. Disable with --disable-pager. This
                      option is disabled by default.
  -p, --password[=name]
                      Password to use when connecting to server. If password is
                      not given it's asked from the tty.
  -P, --port=#        Port number to use for connection or 0 for default to, in
                      order of preference, my.cnf, $MYSQL_TCP_PORT,
                      /etc/services, built-in default (3306).
  --prompt=name       Set the mysql prompt to this value.
  --protocol=name     The protocol to use for connection (tcp, socket, pipe,
                      memory).
  -q, --quick         Don't cache result, print it row by row. This may slow
                      down the server if the output is suspended. Doesn't use
                      history file.
  -r, --raw           Write fields without conversion. Used with --batch.
  --reconnect         Reconnect if the connection is lost. Disable with
                      --disable-reconnect. This option is enabled by default.
                      (Defaults to on; use --skip-reconnect to disable.)
  -s, --silent        Be more silent. Print results with a tab as separator,
                      each row on new line.
  -S, --socket=name   The socket file to use for connection.
  --server-public-key-path=name
                      File path to the server public RSA key in PEM format.
  --get-server-public-key
                      Get server public key
  --ssl-mode=name     SSL connection mode.
  --ssl-ca=name       CA file in PEM format.
  --ssl-capath=name   CA directory.
  --ssl-cert=name     X509 cert in PEM format.
  --ssl-cipher=name   SSL cipher to use.
  --ssl-key=name      X509 key in PEM format.
  --ssl-crl=name      Certificate revocation list.
  --ssl-crlpath=name  Certificate revocation list path.
  --tls-version=name  TLS version to use, permitted values are: TLSv1, TLSv1.1,
                      TLSv1.2, TLSv1.3
  --ssl-fips-mode=name
                      SSL FIPS mode (applies only for OpenSSL); permitted
                      values are: OFF, ON, STRICT
  --tls-ciphersuites=name
                      TLS v1.3 cipher to use.
  -t, --table         Output in table format.
  --tee=name          Append everything into outfile. See interactive help (\h)
                      also. Does not work in batch mode. Disable with
                      --disable-tee. This option is disabled by default.
  -u, --user=name     User for login if not current user.
  -U, --safe-updates  Only allow UPDATE and DELETE that uses keys.
  -U, --i-am-a-dummy  Synonym for option --safe-updates, -U.
  -v, --verbose       Write more. (-v -v -v gives the table output format).
  -V, --version       Output version information and exit.
  -w, --wait          Wait and retry if connection is down.
  --connect-timeout=# Number of seconds before connection timeout.
  --max-allowed-packet=#
                      The maximum packet length to send to or receive from
                      server.
  --net-buffer-length=#
                      The buffer size for TCP/IP and socket communication.
  --select-limit=#    Automatic limit for SELECT when using --safe-updates.
  --max-join-size=#   Automatic limit for rows in a join when using
                      --safe-updates.
  --show-warnings     Show warnings after every statement.
  -j, --syslog        Log filtered interactive commands to syslog. Filtering of
                      commands depends on the patterns supplied via histignore
                      option besides the default patterns.
  --plugin-dir=name   Directory for client-side plugins.
  --default-auth=name Default authentication client-side plugin to use.
  --binary-mode       By default, ASCII '\0' is disallowed and '\r\n' is
                      translated to '\n'. This switch turns off both features,
                      and also turns off parsing of all clientcommands except
                      \C and DELIMITER, in non-interactive mode (for input
                      piped to mysql or loaded using the 'source' command).
                      This is necessary when processing output from mysqlbinlog
                      that may contain blobs.
  --connect-expired-password
                      Notify the server that this client is prepared to handle
                      expired password sandbox mode.
  --network-namespace=name
                      Network namespace to use for connection via tcp with a
                      server.
  --compression-algorithms=name
                      Use compression algorithm in server/client protocol.
                      Valid values are any combination of
                      'zstd','zlib','uncompressed'.
  --zstd-compression-level=#
                      Use this compression level in the client/server protocol,
                      in case --compression-algorithms=zstd. Valid range is
                      between 1 and 22, inclusive. Default is 3.
  --load-data-local-dir=name
                      Directory path safe for LOAD DATA LOCAL INFILE to read
                      from.

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf
The following groups are read: mysql client
The following options may be given as the first argument:
--print-defaults        Print the program argument list and exit.
--no-defaults           Don't read default options from any option file,
                        except for login file.
--defaults-file=#       Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=#
                        Also read groups with concat(group, suffix)
--login-path=#          Read this path from the login file.

Variables (--variable-name=value)
and boolean options {FALSE|TRUE}  Value (after reading options)
--------------------------------- ----------------------------------------
auto-rehash                       TRUE
auto-vertical-output              FALSE
bind-address                      (No default value)
binary-as-hex                     FALSE
character-sets-dir                (No default value)
column-type-info                  FALSE
comments                          FALSE
compress                          FALSE
database                          (No default value)
default-character-set             auto
delimiter                         ;
enable-cleartext-plugin           FALSE
vertical                          FALSE
force                             FALSE
histignore                        (No default value)
named-commands                    FALSE
ignore-spaces                     FALSE
init-command                      (No default value)
local-infile                      FALSE
no-beep                           FALSE
host                              (No default value)
dns-srv-name                      (No default value)
html                              FALSE
xml                               FALSE
line-numbers                      TRUE
unbuffered                        FALSE
column-names                      TRUE
sigint-ignore                     FALSE
port                              0
prompt                            mysql>
quick                             FALSE
raw                               FALSE
reconnect                         TRUE
socket                            (No default value)
server-public-key-path            (No default value)
get-server-public-key             FALSE
ssl-ca                            (No default value)
ssl-capath                        (No default value)
ssl-cert                          (No default value)
ssl-cipher                        (No default value)
ssl-key                           (No default value)
ssl-crl                           (No default value)
ssl-crlpath                       (No default value)
tls-version                       (No default value)
tls-ciphersuites                  (No default value)
table                             FALSE
user                              (No default value)
safe-updates                      FALSE
i-am-a-dummy                      FALSE
connect-timeout                   0
max-allowed-packet                16777216
net-buffer-length                 16384
select-limit                      1000
max-join-size                     1000000
show-warnings                     FALSE
plugin-dir                        (No default value)
default-auth                      (No default value)
binary-mode                       FALSE
connect-expired-password          FALSE
network-namespace                 (No default value)
compression-algorithms            (No default value)
zstd-compression-level            3
load-data-local-dir               (No default value)

#常用选项
-V|--version #显示客户端版本
-u|--user=name #指定远程连接用户名
-p|--password[=name] #指定密码，默认为空
-h|--host=host #指定服务端主机
-P|--port=port #指定端口，默认3306
-S|--socket=name #指定连接时使用的socket文件，该文件在服务端启动后生成
-D|--database=db #指定数据库
-H|--html #以html格式输出
-X|--xml #以xml格式输出
-t|--table #以table格式输出，默认项
-E|--vertical #垂直显示执行结果
-v|--verbose #显示详细信息，配合-t选项
-C|--compress #启用压缩
-G|--named-commands #启用长命令
-e|--execute=sql #执行完就退出，非交互式运行
-prompt=name #修改命令提示符
--line-numbers #输出行号
--print-defaults #打印参数列表，放在最前面
--connect-timeout=N #连接超时时长，单位S
--max-allowed-packet=N #一次查交互发送或反回数据的大小，默认16MB，最大值为1GB，最小值为4096字节

范例：

#免密登录
[root@localhost ~ 10:02:01]# mysql -uroot -p123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.


`mysql> alter user root@localhost identified by '';`
Query OK, 0 rows affected (0.00 sec)

#显示版本
[root@localhost ~ 10:03:27]# mysql -V
mysql  Ver 8.0.26 for Linux on x86_64 (Source distribution)

#指定用户名，主机，端口
[root@localhost ~ 10:03:33]# mysql -uroot -h127.0.0.1 -P3306
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

#使用主机名
[root@localhost ~ 10:03:56]# mysql --user=root --host=localhost --port=3306
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 11
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>


#默认使用root连接，密码为空
[root@localhost ~ 10:04:22]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

#打印参数列表，并不连接服务端，--print-defaults要放在第一个
[root@localhost ~ 10:04:32]# mysql --print-defaults -uroot -hlocalhost --connect-timeout=2
mysql would have been started with the following arguments:
-uroot -hlocalhost --connect-timeout=2

#以html格式显示输出
[root@localhost ~ 10:05:08]# mysql -H
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> select version();
<TABLE BORDER=1><TR><TH>version()</TH></TR><TR><TD>8.0.26</TD></TR></TABLE>1 row in set (0.00 sec)

[root@localhost ~ 10:05:41]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 14
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

范例：执行完退出，非交互式执行

#环境准备
[root@localhost ~ 10:41:51]# vim /root/test.sql
[root@localhost ~ 10:42:32]# cat /root/test.sql
show databases;

#执行客户端命令
[root@localhost ~ 10:42:35]# mysql -e "source /root/test.sql"
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

#管道执行
[root@localhost ~ 10:42:53]# cat test.sql |mysql
Database
information_schema
mysql
performance_schema
sys

#标准输入重定向执行
[root@localhost ~ 10:43:04]# mysql -uroot < test.sql
Database
information_schema
mysql
performance_schema
sys

#以table格式输出
[root@localhost ~ 10:43:19]# mysql -e "show databases;"
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

#垂直显示
[root@localhost ~ 10:43:33]# mysql -e "show databases;" -E
*************************** 1. row ***************************
Database: information_schema
*************************** 2. row ***************************
Database: mysql
*************************** 3. row ***************************
Database: performance_schema
*************************** 4. row ***************************
Database: sys

[root@localhost ~ 10:43:40]# mysql -e "show databases;" -X
<?xml version="1.0"?>

<resultset statement="show databases" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <row>
        <field name="Database">information_schema</field>
  </row>

  <row>
        <field name="Database">mysql</field>
  </row>

  <row>
        <field name="Database">performance_schema</field>
  </row>

  <row>
        <field name="Database">sys</field>
  </row>
</resultset>

范例：修改提示符

[root@localhost ~ 10:43:47]# mysql --prompt=[test]
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 21
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

[test]quit
Bye
[root@localhost ~ 10:44:07]# mysql --prompt='[test] '
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 22
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

[test] quit
Bye

范例：指定数据库

#默认
[root@localhost ~ 10:44:19]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 23
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

mysql> quit
Bye

#指定数据库
[root@localhost ~ 10:44:41]# mysql information_schema
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 24
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> select database();
+--------------------+
| database()         |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)

mysql> quit
Bye

[root@localhost ~ 10:45:14]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 25
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> select database();
+------------+
| database() |
+------------+
| NULL       |
+------------+
1 row in set (0.00 sec)

mysql> quit
Bye

2.4.4.2 MySQL客户端常用命令

mysql> ?

For information about MySQL products and services, visit:
   http://www.mysql.com/
For developer information, including the MySQL Reference Manual, visit:
   http://dev.mysql.com/
To buy MySQL Enterprise support, training, or other products, visit:
   https://shop.mysql.com/

List of all MySQL commands:
Note that all text commands must be first on line and end with ';'
?         (\?) Synonym for `help'.
clear     (\c) Clear the current input statement.
connect   (\r) Reconnect to the server. Optional arguments are db and host.
delimiter (\d) Set statement delimiter.
edit      (\e) Edit command with $EDITOR.
ego       (\G) Send command to mysql server, display result vertically.
exit      (\q) Exit mysql. Same as quit.
go        (\g) Send command to mysql server.
help      (\h) Display this help.
nopager   (\n) Disable pager, print to stdout.
notee     (\t) Don't write into outfile.
pager     (\P) Set PAGER [to_pager]. Print the query results via PAGER.
print     (\p) Print current command.
prompt    (\R) Change your mysql prompt.
quit      (\q) Quit mysql.
rehash    (\#) Rebuild completion hash.
source    (\.) Execute an SQL script file. Takes a file name as an argument.
status    (\s) Get status information from the server.
system    (\!) Execute a system shell command.
tee       (\T) Set outfile [to_outfile]. Append everything into given outfile.
use       (\u) Use another database. Takes database name as argument.
charset   (\C) Switch to another charset. Might be needed for processing binlog with multi-byte charsets.
warnings  (\W) Show warnings after every statement.
nowarning (\w) Don't show warnings after every statement.
resetconnection(\x) Clean session context.
query_attributes Sets string parameters (name1 value1 name2 value2 ...) for the next query to pick up.

For server side help, type 'help contents'

范例：显示当前数据库

#显示当前数据库
mysql> \s
--------------
mysql  Ver 8.0.26 for Linux on x86_64 (Source distribution)

#连接ID
Connection id:          36
#当前使用的数据库
Current database:
#连接使用的用户名
Current user:           root@localhost
#是否使用ssl
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
#版本
Server version:         8.0.26 Source distribution
#协议版本
Protocol version:       10
Connection:             Localhost via UNIX socket
#服务器编码
Server characterset:    utf8mb4
#数据库编码
Db     characterset:    utf8mb4
#客户端编码
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
#连接使用的socket文件
UNIX socket:            /var/lib/mysql/mysql.sock
Binary data as:         Hexadecimal
#服务器运行时长
Uptime:                 2 hours 3 min 48 sec

Threads: 2  Questions: 220  Slow queries: 0  Opens: 275  Flush tables: 3  Open tables: 194  Queries per second avg: 0.029
--------------

范例：切换数据库

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

范例：调用系统命令

#查看宿主机主机名，！号后面有空格
mysql> \! hostname
localhost.localdomain
mysql> system hostname
localhost.localdomain

#清屏
mysql> \! clear

范例：修改提示符

mysql> prompt [\h--\d]
PROMPT set to '[\h--\d]'
[localhost--mysql]\R abcd
PROMPT set to 'abcd'
abcdquit
Bye

在配置文件中修改提示符

#主机的提示符
[root@localhost ~ 11:01:02]# set |grep PS
GROUPS=()
PS1='[\[\e[91m\]\u\[\e[93m\]@\[\e[92;1m\]\h\[\e[0m\] \[\e[94m\]\W\[\e[0m\] \[\e[35m\]\t\[\e[0m\]]\[\e[93m\]\$\[\e[0m\] '
PS2='> '
PS4='+ '

[root@localhost ~ 11:01:14]# vim /etc/my.cnf.d/client.cnf
#
# These two groups are read by the client library
# Use it for options that affect all clients, but not the server
#


[client]
prompt=(\\u@\\h) [\\d]>\\

# This group is not read by mysql client library,
# If you use the same .cnf file for MySQL and MariaDB,
# use it for MariaDB-only client options
[client-mariadb]

#验证效果
[root@localhost ~ 11:05:12]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 29
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

`(root@localhost) [(none)] >`

提示符中可用的变量，全部可用的替换符用man sql查看

\C #计数器
\D #年月日时分秒
\d #当前使用的数据库
\h #服务器主机名
\l #命令分隔符，默认；
\m #当前时间，分钟
\n #换行
\O #月份，以英文显示
\o #月份，数字显示
\P #pm/am
\R #小时，24小时制
\r #小时，12小时制
\S #分号
\s #秒，数字显示
\t #tab键
\U #客户端用户名和主机
\u #客户端用户名
\v #服务端版本
\w #星期几，英文显示
\Y #年份，四位，数字显示
\y #年份，两位，数字显示

范例：执行SQL脚本

[root@localhost ~ 11:39:54]# cat test.sql
show databases;

[root@localhost ~ 11:40:09]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 31
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> \. /root/test.sql
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

范例：重连

mysql> \r
Connection id:    32
Current database: *** NONE ***

mysql> \r
Connection id:    33
Current database: *** NONE ***

范例：往文件中保存输出结果

#设置写到文件db.txt
mysql> tee db.txt
Logging to file 'db.txt'

#执行SQL语句
mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

#设置不写文件
mysql> \t
Outfile disabled.
mysql> quit
Bye

#只记录了\t之前的命令
[root@localhost ~ 11:41:17]# cat db.txt
mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

mysql> \t

范例：自定义

#两条查询语句，默认用;分隔
[root@localhost ~ 11:41:20]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 34
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.


mysql> select version();show databases;
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.01 sec)

+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

#设置$分隔
mysql> \d $
mysql> select version()$show databases$
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

#修改回来
mysql> \d ;

范例：发送语句到服务端

mysql> select version();
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

mysql> select version()\g
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

mysql> select version()\G
*************************** 1. row ***************************
version(): 8.0.26
1 row in set (0.00 sec)

mysql> quit
Bye

#开启长命令格式
[root@localhost ~ 11:42:47]# mysql --named-commands
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 35
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> select version()
    -> go
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

mysql> select version()
    -> ego
*************************** 1. row ***************************
version(): 8.0.26
1 row in set (0.00 sec)

范例：只输出不执行

mysql> select version()\p
--------------
select version()
--------------

    -> show databases
    -> quit
Bye

2.4.4.3 mysqladmin工具

mysqladmin也是用于管理mysql服务的本地工具

格式

[root@localhost ~ 14:00:16]# mysqladmin --help
mysqladmin  Ver 8.0.26 for Linux on x86_64 (Source distribution)
Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Administration program for the mysqld daemon.
Usage: mysqladmin [OPTIONS] command command....
  --bind-address=name IP address to bind to.
  #总共执行多少次，配合-i选项使用
  -c, --count=#       Number of iterations to make. This works with -i
                      (--sleep) only.
  -#, --debug[=#]     This is a non-debug version. Catch this and exit.
  --debug-check       This is a non-debug version. Catch this and exit.
  --debug-info        This is a non-debug version. Catch this and exit.
  -f, --force         Don't ask for confirmation on drop database; with
                      multiple commands, continue even if an error occurs.
  #启用压缩
  -C, --compress      Use compression in server/client protocol.
  --character-sets-dir=name
                      Directory for character set files.
  --default-character-set=name
                      Set the default character set.
  #显示帮助信息
  -?, --help          Display this help and exit.
  #指定服务器地址
  -h, --host=name     Connect to host.
  -b, --no-beep       Turn off beep on error.
  #指定连接服务器的密码
  -p, --password[=name]
                      Password to use when connecting to server. If password is
                      not given it's asked from the tty.
  #指定服务器端口，默认3306
  -P, --port=#        Port number to use for connection or 0 for default to, in
                      order of preference, my.cnf, $MYSQL_TCP_PORT,
                      /etc/services, built-in default (3306).
  #指定连接方式(tcp\socket\pipe\memory)
  --protocol=name     The protocol to use for connection (tcp, socket, pipe,
                      memory).
  -r, --relative      Show difference between current and previous values when
                      used with -i. Currently only works with extended-status.
  #如果无法连接，则静默退出
  -s, --silent        Silently exit if one can't connect to server.
  #指定连接时使用socket文件
  -S, --socket=name   The socket file to use for connection.
  #持续执行命令，间隔N秒执行一次
  -i, --sleep=#       Execute commands repeatedly with a sleep between.
  --ssl-mode=name     SSL connection mode.
  --ssl-ca=name       CA file in PEM format.
  --ssl-capath=name   CA directory.
  --ssl-cert=name     X509 cert in PEM format.
  --ssl-cipher=name   SSL cipher to use.
  --ssl-key=name      X509 key in PEM format.
  --ssl-crl=name      Certificate revocation list.
  --ssl-crlpath=name  Certificate revocation list path.
  --tls-version=name  TLS version to use, permitted values are: TLSv1, TLSv1.1,
                      TLSv1.2, TLSv1.3
  --ssl-fips-mode=name
                      SSL FIPS mode (applies only for OpenSSL); permitted
                      values are: OFF, ON, STRICT
  --tls-ciphersuites=name
                      TLS v1.3 cipher to use.
  --server-public-key-path=name
                      File path to the server public RSA key in PEM format.
  --get-server-public-key
                      Get server public key
  #指定用户名
  -u, --user=name     User for login if not current user.
  -v, --verbose       Write more information.
  #显示客户端版本
  -V, --version       Output version information and exit.
  -E, --vertical      Print output vertically. Is similar to --relative, but
                      prints output vertically.
  #如果连接失败，是否等待重试，如果指定了具体数字，则表示重试几次
  -w, --wait[=#]      Wait and retry if connection is down.
  #指定连接超时时长
  --connect-timeout=#
  #指定关机超时时长
  --shutdown-timeout=#
  #客户端插件目录
  --plugin-dir=name   Directory for client-side plugins.
  --default-auth=name Default authentication client-side plugin to use.
  --enable-cleartext-plugin
                      Enable/disable the clear text authentication plugin.
  --show-warnings     Show warnings after execution
  --compression-algorithms=name
                      Use compression algorithm in server/client protocol.
                      Valid values are any combination of
                      'zstd','zlib','uncompressed'.
  --zstd-compression-level=#
                      Use this compression level in the client/server protocol,
                      in case --compression-algorithms=zstd. Valid range is
                      between 1 and 22, inclusive. Default is 3.

Variables (--variable-name=value)
and boolean options {FALSE|TRUE}  Value (after reading options)
--------------------------------- ----------------------------------------
bind-address                      (No default value)
count                             0
force                             FALSE
compress                          FALSE
character-sets-dir                (No default value)
default-character-set             auto
host                              (No default value)
no-beep                           FALSE
port                              0
relative                          FALSE
socket                            (No default value)
sleep                             0
ssl-ca                            (No default value)
ssl-capath                        (No default value)
ssl-cert                          (No default value)
ssl-cipher                        (No default value)
ssl-key                           (No default value)
ssl-crl                           (No default value)
ssl-crlpath                       (No default value)
tls-version                       (No default value)
tls-ciphersuites                  (No default value)
server-public-key-path            (No default value)
get-server-public-key             FALSE
user                              (No default value)
verbose                           FALSE
vertical                          FALSE
connect-timeout                   43200
shutdown-timeout                  3600
plugin-dir                        (No default value)
default-auth                      (No default value)
enable-cleartext-plugin           FALSE
show-warnings                     FALSE
compression-algorithms            (No default value)
zstd-compression-level            3

Default options are read from the following files in the given order:
/etc/my.cnf /etc/mysql/my.cnf ~/.my.cnf
The following groups are read: mysqladmin client
The following options may be given as the first argument:
#显示运行参数
--print-defaults        Print the program argument list and exit.
--no-defaults           Don't read default options from any option file,
                        except for login file.
#从指定文件中读取选项
--defaults-file=#       Only read default options from the given file #.
--defaults-extra-file=# Read this file after the global files are read.
--defaults-group-suffix=#
                        Also read groups with concat(group, suffix)
--login-path=#          Read this path from the login file.

Where command is a one or more of: (Commands may be shortened)
  #创建新的数据库
  create databasename   Create a new database
  #开启调试模式，将调试信息写入log
  debug                 Instruct server to write debug information to log
  #删除指定数据库
  drop databasename     Delete a database and all its tables
  #显示扩展状态
  extended-status       Gives an extended status message from the server
  #刷新所有缓存的主机
  flush-hosts           Flush all cached hosts
  #刷新所有日志
  flush-logs            Flush all logs
  #刷新状态变量
  flush-status          Clear status variables
  #刷新所有表，会强制关闭已打开的表
  flush-tables          Flush all tables
 #刷新线程缓存
 flush-threads         Flush the thread cache
  #刷新访问权限
  flush-privileges      Reload grant tables (same as reload)
  kill id,id,...        Kill mysql threads
  password [new-password] Change old password to new-password in current format
  #心跳检测
  ping                  Check if mysqld is alive
  #显示活动线程列表
  processlist           Show list of active threads in server
  #刷新授权信息
  reload                Reload grant tables
  #刷新所有数据库表，重新打开日志文件
  refresh               Flush all tables and close and open logfiles
  #关闭服务
  shutdown              Take server down
  #简短显示服务端状态
  status                Gives a short status message from the server
  start-replica         Start replication
  #开启主从同步
  start-slave           Deprecated: use start-replica instead
  stop-replica          Stop replication
  #停止主从同步
  stop-slave            Deprecated: use stop-replica instead
  #显示服务端所有变量
  variables             Prints variables available
  #显示客户端和服务端版本
  version               Get version info from server

范例：显示版本信息

#客户端版本
[root@localhost ~ 14:00:33]# mysqladmin -V
mysqladmin  Ver 8.0.26 for Linux on x86_64 (Source distribution)

[root@localhost ~ 14:00:48]# mysql -V
mysql  Ver 8.0.26 for Linux on x86_64 (Source distribution)

范例：显示状态信息

[root@localhost ~ 14:00:52]# mysqladmin status
Uptime: 15550  Threads: 2  Questions: 222  Slow queries: 0  Opens: 275  Flush tables: 3  Open tables: 194  Queries per second avg: 0.014

范例：设置连接超时

[root@localhost ~ 14:01:47]# mysqladmin -h1.2.3.4 --connect-timeout=2 ping
emysqladmin: connect to server at '1.2.3.4' failed
error: 'Can't connect to MySQL server on '1.2.3.4:3306' (110)'
Check that mysqld is running on 1.2.3.4 and that the port is 3306.
You can check this by doing 'telnet 1.2.3.4 3306'
[root@localhost ~ 14:01:54]# echo $?
1

#静默退出，不输出错误信息
[root@localhost ~ 14:01:59]# mysqladmin -h1.2.3.4 --connect-timeout=2 -s ping
[root@localhost ~ 14:02:04]# echo $?
1

范例：持续执行

#每秒执行一次ping命令，一直执行下去
[root@localhost ~ 14:02:05]# mysqladmin -i 1 ping
mysqld is alive
mysqld is alive
mysqld is alive
mysqld is alive
... ...

#每秒执行一次ping命令，总共执行3次
[root@localhost ~ 14:02:19]# mysqladmin -i 1 -c 3 ping
mysqld is alive
mysqld is alive
mysqld is alive

范例：关闭服务

#mysqladmin只能关闭服务，不能启动服务
[root@localhost ~ 14:02:27]# mysqladmin shutdown

[root@localhost ~ 14:02:38]# mysqladmin ping
mysqladmin: connect to server at 'localhost' failed
error: 'Can't connect to local MySQL server through socket '/var/lib/mysql/mysql.sock' (2)'
Check that mysqld is running and that the socket: '/var/lib/mysql/mysql.sock' exists!

[root@localhost ~ 14:02:46]# echo $?
1

[root@localhost ~ 14:03:02]# systemctl start mysqld

[root@localhost ~ 14:03:08]# mysqladmin ping
mysqld is alive

范例：创建数据库和删除数据库

#创建
[root@localhost ~ 14:03:18]# mysqladmin create mysqladmin-db1
[root@localhost ~ 14:03:34]# mysqladmin create mysqladmin-db2
[root@localhost ~ 14:03:37]# mysql -e 'show databases;'
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| mysqladmin-db1     |
| mysqladmin-db2     |
| performance_schema |
| sys                |
+--------------------+

#删除
[root@localhost ~ 14:03:48]# mysqladmin drop mysqladmin-db1
Dropping the database is potentially a very bad thing to do.
Any data stored in the database will be destroyed.

#回答y确认
Do you really want to drop the 'mysqladmin-db1' database [y/N] `y`
Database "mysqladmin-db1" dropped

#强制删除，不需要确认
[root@localhost ~ 14:03:48]# mysqladmin -f drop mysqladmin-db1

#验证mysqladmin-db1和mysqladmin-db2已经删除
[root@localhost ~ 14:04:09]# mysqladmin drop mysqladmin-db2
Dropping the database is potentially a very bad thing to do.
Any data stored in the database will be destroyed.

Do you really want to drop the 'mysqladmin-db2' database [y/N] y
Database "mysqladmin-db2" dropped
[root@localhost ~ 14:04:12]# mysql -e 'show databases;'
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

范例：修改连接密码

#旧密码为空，root用户，localhost主机连接
#设置密码为123456
[root@localhost ~ 14:04:15]# mysqladmin password 123456
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.

#不使用密码不行
[root@localhost ~ 14:04:30]# mysqladmin ping
mysqladmin: connect to server at 'localhost' failed
error: 'Access denied for user 'root'@'localhost' (using password: NO)'

#使用密码
[root@localhost ~ 14:04:43]# mysqladmin -uroot -p123456 -hlocalhost ping
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
mysqld is alive

#用旧密码修改新密码
#更改密码为abcde
[root@localhost ~ 14:05:14]# mysqladmin -uroot -p123456 -hlocalhost password abcde
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.

#使用原密码测试不行
[root@localhost ~ 14:05:28]# mysqladmin -uroot -p123456 -hlocalhost ping
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
mysqladmin: connect to server at 'localhost' failed
error: 'Access denied for user 'root'@'localhost' (using password: YES)'

#使用新密码测试
[root@localhost ~ 14:05:33]# mysqladmin -uroot -pabcde -hlocalhost ping
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
mysqld is alive

2.4.4.4 mycli 工具

MyCLI是基于Python开发的MySQL的命令行工具，具有自动完成和语法突出显示功能

#补全命令
[root@localhost ~ 14:06:20]# yum install -y bash-completion
[root@localhost ~ 14:19:51]# yum install -y python39
[root@localhost ~ 14:20:20]# pip3.9 config set global.index-url https://pypi.tuna.tsinghua.edu.cn/simple
Writing to /root/.config/pip/pip.conf
[root@localhost ~ 14:20:31]# pip-3.9 install mycli

#使用
[root@localhost ~ 14:21:10]# mycli
Connecting to socket /var/lib/mysql/mysql.sock, owned by user mysql
MySQL
mycli 1.38.4
Home: http://mycli.net
Bug tracker: https://github.com/dbcli/mycli/issues
Thanks to the contributor - Fabrizio Gennari
MySQL root@(none):(none)> show databases
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

4 rows in set
Time: 0.008s
MySQL root@(none):(none)> quit
Goodbye!

#关机打快照
[root@localhost ~ 14:21:40]# poweroff

3 SQL语言

3.1关系型数据库的构成

3.2 SQL语言介绍

SQL:（Structured Query Language）结构化查询语言。

• SQL语言是对IBM公司San Jose,California研究实验室的埃德加·科德的关系模型的第一个商业化语言实现。尽管SQL并非完全按照科德的关系模型设计，但其依然成为最为广泛运用的数据库语言

• 1970年代初，由埃德加·科德发表将资料组成表格的应用原则（Codd's Relational Algebra）。

• 1974年，同一实验室的D.D.Chamberlin 和 R.F.Boyce对Codd's Relational Algebra在研制关系数据库管理系统System R中，研制出一套规范语言SEQUEL(Structured English Query Language)。

• 1976年11月的IBM Journal of R&D上公布新版本的 SQL(叫SEQUEL/2)。1980年改名为SQL。

• 1979年ORACLE公司首先提供商用的SQL，IBM公司在DB2和SQL/DS数据库系统中也实现了SQL。

• 1986年10月美国国家标准学会ANSI采用SQL作为关系数据库管理系统的标准语言（ANSIX3.135-1986)。

• 1987年成为国际标准化组织（(ISO）采纳为国际标准。

• 1989年美国ANSI采纳在ANSIX3.135-1989报告中定义的关系数据库管理系统的SQL标准语言，称为ANSI SQL 89。

• 后续SQL标准经过了一系列的增订，加入了大量新特性，有各种版本：ANSISQL，SQL-1986，SQL-1989，SQL-1992，SQL-1999，SQL-2003，SQL-2008，SQL-2011。

• 目前，所有主要的关系数据库管理系统支持某些形式的SQL，大部分数据库至少遵守ANSISQL89标准。

• 虽然有这一标准的存在，但大部分的SQL代码在不同的数据库系统中并不具有完全的跨平台性。

• 业内标准微软和 Sybase 的T-SQL，Oracle 的 PL/SQL。

3.2.1 SQL语言规范

• 在数据库系统中，SQL语句不区分大小写，建议用大写。

• SQL语句可单行或多行书写，默认以 **；**结尾。

• 关键词不能跨多行或简写。

• 用空格和TAB缩进来提高语句的可读性。

• 子句通常位于独立行，便于编辑，提高可读性。

#不区分大小写
[root@localhost ~ 14:50:22]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

`mysql> select @@hostname;`
+-----------------------+
| @@hostname            |
+-----------------------+
| localhost.localdomain |
+-----------------------+
1 row in set (0.00 sec)

`mysql> SELect @@HOSTname;`
+-----------------------+
| @@HOSTname            |
+-----------------------+
| localhost.localdomain |
+-----------------------+
1 row in set (0.00 sec)

`mysql> SELECT @@HOSTNAME;`
+-----------------------+
| @@HOSTNAME            |
+-----------------------+
| localhost.localdomain |
+-----------------------+
1 row in set (0.00 sec)

#区分大小写
`mysql> select user,host from mysql.user;`
+------------------+-----------+
| user             | host      |
+------------------+-----------+
| mysql.infoschema | localhost |
| mysql.session    | localhost |
| mysql.sys        | localhost |
| root             | localhost |
+------------------+-----------+
4 rows in set (0.00 sec)

`mysql> SElect user,host from mysql.user;`
+------------------+-----------+
| user             | host      |
+------------------+-----------+
| mysql.infoschema | localhost |
| mysql.session    | localhost |
| mysql.sys        | localhost |
| root             | localhost |
+------------------+-----------+
4 rows in set (0.00 sec)

`mysql> SElect user,host from mysql.USER;`
ERROR 1146 (42S02): Table 'mysql.USER' doesn't exist


#字段不区分大小写，库名表名区分大小写
`mysql> SELect user,HOST from mysql.user;`
+------------------+-----------+
| user             | HOST      |
+------------------+-----------+
| mysql.infoschema | localhost |
| mysql.session    | localhost |
| mysql.sys        | localhost |
| root             | localhost |
+------------------+-----------+
4 rows in set (0.00 sec)

范例：跨行

`mysql> show databases;`
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

`mysql> show
    -> databases;`
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

#关键字不能跨行
`mysql> show data
    -> bases;`
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'data
bases' at line 1

SQL语言中的注释

SQL语言中的标准注释

mysql> --select version()\G
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '--select version()' at line 1
`mysql> -- select version()\G
`mysql> /*
  ` /*> select version()\g`
   `/*> select version()\g`
  ` /*> */`
`mysql> select version()\g``
+-----------+
| version() |
+-----------+
| 8.0.26    |
+-----------+
1 row in set (0.00 sec)

范例：

[root@localhost ~ 14:53:45]# vim test.sql
[root@localhost ~ 14:54:20]# cat test.sql
-- select version()\G
/*
select version()\G
select version()\G
*/
select version()\G
[root@localhost ~ 14:54:23]# mysql < test.sql
*************************** 1. row ***************************
version(): 8.0.26

MySQL中的注释

# select version()\G #MySQL中的注释
select version()\G

3.2.2数据库对象和命名

数据库中的组件（对象）

数据库、表、索引、视图、用户、存储过程、函数、触发器、事件调度器等

组件命名规则

• 可以包括字母，数字和三个特殊字符（#_$）

• 不能使用MySQL的保留字

3.2.3 SQL语句分类

SQL语句类型	说明	具体语句
DDL	Data Defination Language数据定义语言	CREATE，DROP，ALTER
DML	Data Mainpulation Language数据操纵语言	INSERT，DELETE，UPDATE
DQL	Data Query Language数据查询语言	SELECT
DCL	Data Control Language数据控制语言	GRANT，REVOKE
TCL	Transaction Control Language事务控制语言	BEGIN，COMMIT，ROLLBACK，SAVEPOINT

3.2.4 SQL语句构成

关键字keyword组成子句clause，多条clause组成语句

[root@localhost ~ 15:13:05]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> select host,user,authentication_string from mysql.user where authentication_string='';
+-----------+------+-----------------------+
| host      | user | authentication_string |
+-----------+------+-----------------------+
| localhost | root |                       |
+-----------+------+-----------------------+
1 row in set (0.01 sec)

说明：

#select子句
select host,user,authentication_string 
#from子句
from mysql.user 
#where子句
where authentication_string='';

命令行下查看帮助

mysql> help contents;
You asked for help about help category: "Contents"
For more information, type 'help <item>', where <item> is one of the following
categories:
   Account Management
   Administration
   Components
   Compound Statements
   Contents
   Data Definition
   Data Manipulation
   Data Types
   Functions
   Geographic Features
   Help Metadata
   Language Structure
   Loadable Functions
   Plugins
   Prepared Statements
   Replication Statements
   Storage Engines
   Table Maintenance
   Transactions
   Utility

#查看DDL帮助
mysql> help Data Definition;
You asked for help about help category: "Data Definition"
For more information, type 'help <item>', where <item> is one of the following
topics:
   ALTER DATABASE
   ALTER EVENT
   ALTER FUNCTION
   ALTER INSTANCE
   ALTER LOGFILE GROUP
   ALTER PROCEDURE
   ALTER SCHEMA
   ALTER SERVER
   ALTER TABLE
   ALTER TABLESPACE
   ALTER VIEW
   CREATE DATABASE
   CREATE EVENT
   CREATE FUNCTION
   CREATE INDEX
   CREATE LOGFILE GROUP
   CREATE PROCEDURE
   CREATE SCHEMA
   CREATE SERVER
   CREATE SPATIAL REFERENCE SYSTEM
   CREATE TABLE
   CREATE TABLESPACE
   CREATE TRIGGER
   CREATE VIEW
   DROP DATABASE
   DROP EVENT
   DROP FUNCTION
   DROP INDEX
   DROP PROCEDURE
   DROP SCHEMA
   DROP SERVER
   DROP SPATIAL REFERENCE SYSTEM
   DROP TABLE
   DROP TABLESPACE
   DROP TRIGGER
   DROP VIEW
   FOREIGN KEY
   RENAME TABLE
   TRUNCATE TABLE

mysql> help CREATE DATABASE;
Name: 'CREATE DATABASE'
Description:
Syntax:
CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
    [create_option] ...

create_option: [DEFAULT] {
    CHARACTER SET [=] charset_name
  | COLLATE [=] collation_name
  | ENCRYPTION [=] {'Y' | 'N'}
}

CREATE DATABASE creates a database with the given name. To use this
statement, you need the CREATE privilege for the database. CREATE
SCHEMA is a synonym for CREATE DATABASE.

URL: https://dev.mysql.com/doc/refman/8.0/en/create-database.html

3.2.5字符集和排序

早期MySQL版本默认为latin1，从MySQL8.0开始默认字符集已经为utf8mb4

查看当前版本可用的字符集

#查看所有支持的字符集
mysql> show character set;
+----------+---------------------------------+---------------------+--------+
| Charset  | Description                     | Default collation   | Maxlen |
+----------+---------------------------------+---------------------+--------+
| armscii8 | ARMSCII-8 Armenian              | armscii8_general_ci |      1 |
| ascii    | US ASCII                        | ascii_general_ci    |      1 |
| big5     | Big5 Traditional Chinese        | big5_chinese_ci     |      2 |
| binary   | Binary pseudo charset           | binary              |      1 |
| cp1250   | Windows Central European        | cp1250_general_ci   |      1 |
| cp1251   | Windows Cyrillic                | cp1251_general_ci   |      1 |
| cp1256   | Windows Arabic                  | cp1256_general_ci   |      1 |
| cp1257   | Windows Baltic                  | cp1257_general_ci   |      1 |
| cp850    | DOS West European               | cp850_general_ci    |      1 |
| cp852    | DOS Central European            | cp852_general_ci    |      1 |
| cp866    | DOS Russian                     | cp866_general_ci    |      1 |
| cp932    | SJIS for Windows Japanese       | cp932_japanese_ci   |      2 |
| dec8     | DEC West European               | dec8_swedish_ci     |      1 |
| eucjpms  | UJIS for Windows Japanese       | eucjpms_japanese_ci |      3 |
| euckr    | EUC-KR Korean                   | euckr_korean_ci     |      2 |
| gb18030  | China National Standard GB18030 | gb18030_chinese_ci  |      4 |
| gb2312   | GB2312 Simplified Chinese       | gb2312_chinese_ci   |      2 |
| gbk      | GBK Simplified Chinese          | gbk_chinese_ci      |      2 |
| geostd8  | GEOSTD8 Georgian                | geostd8_general_ci  |      1 |
| greek    | ISO 8859-7 Greek                | greek_general_ci    |      1 |
| hebrew   | ISO 8859-8 Hebrew               | hebrew_general_ci   |      1 |
| hp8      | HP West European                | hp8_english_ci      |      1 |
| keybcs2  | DOS Kamenicky Czech-Slovak      | keybcs2_general_ci  |      1 |
| koi8r    | KOI8-R Relcom Russian           | koi8r_general_ci    |      1 |
| koi8u    | KOI8-U Ukrainian                | koi8u_general_ci    |      1 |
| latin1   | cp1252 West European            | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European     | latin2_general_ci   |      1 |
| latin5   | ISO 8859-9 Turkish              | latin5_turkish_ci   |      1 |
| latin7   | ISO 8859-13 Baltic              | latin7_general_ci   |      1 |
| macce    | Mac Central European            | macce_general_ci    |      1 |
| macroman | Mac West European               | macroman_general_ci |      1 |
| sjis     | Shift-JIS Japanese              | sjis_japanese_ci    |      2 |
| swe7     | 7bit Swedish                    | swe7_swedish_ci     |      1 |
| tis620   | TIS620 Thai                     | tis620_thai_ci      |      1 |
| ucs2     | UCS-2 Unicode                   | ucs2_general_ci     |      2 |
| ujis     | EUC-JP Japanese                 | ujis_japanese_ci    |      3 |
| utf16    | UTF-16 Unicode                  | utf16_general_ci    |      4 |
| utf16le  | UTF-16LE Unicode                | utf16le_general_ci  |      4 |
| utf32    | UTF-32 Unicode                  | utf32_general_ci    |      4 |
| utf8     | UTF-8 Unicode                   | utf8_general_ci     |      3 |
| utf8mb4  | UTF-8 Unicode                   | utf8mb4_0900_ai_ci  |      4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.00 sec)

查看当前默认字符集

mysql> show variables like 'character%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | utf8mb4                    |
| character_set_connection | utf8mb4                    |
| character_set_database   | utf8mb4                    |
| character_set_filesystem | binary                     |
| character_set_results    | utf8mb4                    |
| character_set_server     | utf8mb4                    |
| character_set_system     | utf8mb3                    |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.00 sec)

修改mariadb-server的默认字符集

[root@localhost ~ 15:27:56]# vim /etc/my.cnf.d/mysql-server.cnf
[root@localhost ~ 15:28:34]# tail -1 /etc/my.cnf.d/mysql-server.cnf
character-set-server=latin1

[root@localhost ~ 15:28:38]# vim /etc/my.cnf.d/client.cnf
[root@localhost ~ 15:29:10]# cat /etc/my.cnf.d/client.cnf
#
# These two groups are read by the client library
# Use it for options that affect all clients, but not the server
#


[client]
`default-character-set=latin1`

# This group is not read by mysql client library,
# If you use the same .cnf file for MySQL and MariaDB,
# use it for MariaDB-only client options
[client-mariadb]

#重启服务
[root@localhost ~ 15:29:12]# systemctl restart mysqld

[root@localhost ~ 15:29:26]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show variables like 'character%';
+--------------------------+----------------------------+
| Variable_name            | Value                      |
+--------------------------+----------------------------+
| character_set_client     | latin1                     |
| character_set_connection | latin1                     |
| character_set_database   | latin1                     |
| character_set_filesystem | binary                     |
| character_set_results    | latin1                     |
| character_set_server     | latin1                     |
| character_set_system     | utf8mb3                    |
| character_sets_dir       | /usr/share/mysql/charsets/ |
+--------------------------+----------------------------+
8 rows in set (0.01 sec)
#再改回来

查看当前版本可用的排序规则

mysql> show collation;
+----------------------------+----------+-----+---------+----------+---------+---------------+
| Collation                  | Charset  | Id  | Default | Compiled | Sortlen | Pad_attribute |
+----------------------------+----------+-----+---------+----------+---------+---------------+
| armscii8_bin               | armscii8 |  64 |         | Yes      |       1 | PAD SPACE     |
| armscii8_general_ci        | armscii8 |  32 | Yes     | Yes      |       1 | PAD SPACE     |
| ascii_bin                  | ascii    |  65 |         | Yes      |       1 | PAD SPACE     |
| ascii_general_ci           | ascii    |  11 | Yes     | Yes      |       1 | PAD SPACE     |
| big5_bin                   | big5     |  84 |         | Yes      |       1 | PAD SPACE     |
| big5_chinese_ci            | big5     |   1 | Yes     | Yes      |       1 | PAD SPACE     |
| binary                     | binary   |  63 | Yes     | Yes      |       1 | NO PAD        |
| cp1250_bin                 | cp1250   |  66 |         | Yes      |       1 | PAD SPACE     |
| cp1250_croatian_ci         | cp1250   |  44 |         | Yes      |       1 | PAD SPACE     |
| cp1250_czech_cs            | cp1250   |  34 |         | Yes      |       2 | PAD SPACE     |
| cp1250_general_ci          | cp1250   |  26 | Yes     | Yes      |       1 | PAD SPACE     |
| cp1250_polish_ci           | cp1250   |  99 |         | Yes      |       1 | PAD SPACE     |
| cp1251_bin                 | cp1251   |  50 |         | Yes      |       1 | PAD SPACE     |
| cp1251_bulgarian_ci        | cp1251   |  14 |         | Yes      |       1 | PAD SPACE     |
| cp1251_general_ci          | cp1251   |  51 | Yes     | Yes      |       1 | PAD SPACE     |
| cp1251_general_cs          | cp1251   |  52 |         | Yes      |       1 | PAD SPACE     |
| cp1251_ukrainian_ci        | cp1251   |  23 |         | Yes      |       1 | PAD SPACE     |
| cp1256_bin                 | cp1256   |  67 |         | Yes      |       1 | PAD SPACE     |
| cp1256_general_ci          | cp1256   |  57 | Yes     | Yes      |       1 | PAD SPACE     |
| cp1257_bin                 | cp1257   |  58 |         | Yes      |       1 | PAD SPACE     |
| cp1257_general_ci          | cp1257   |  59 | Yes     | Yes      |       1 | PAD SPACE     |
| cp1257_lithuanian_ci       | cp1257   |  29 |         | Yes      |       1 | PAD SPACE     |
| cp850_bin                  | cp850    |  80 |         | Yes      |       1 | PAD SPACE     |
| cp850_general_ci           | cp850    |   4 | Yes     | Yes      |       1 | PAD SPACE     |
| cp852_bin                  | cp852    |  81 |         | Yes      |       1 | PAD SPACE     |
| cp852_general_ci           | cp852    |  40 | Yes     | Yes      |       1 | PAD SPACE     |
| cp866_bin                  | cp866    |  68 |         | Yes      |       1 | PAD SPACE     |
| cp866_general_ci           | cp866    |  36 | Yes     | Yes      |       1 | PAD SPACE     |
| cp932_bin                  | cp932    |  96 |         | Yes      |       1 | PAD SPACE     |
| cp932_japanese_ci          | cp932    |  95 | Yes     | Yes      |       1 | PAD SPACE     |
| dec8_bin                   | dec8     |  69 |         | Yes      |       1 | PAD SPACE     |
| dec8_swedish_ci            | dec8     |   3 | Yes     | Yes      |       1 | PAD SPACE     |
| eucjpms_bin                | eucjpms  |  98 |         | Yes      |       1 | PAD SPACE     |
| eucjpms_japanese_ci        | eucjpms  |  97 | Yes     | Yes      |       1 | PAD SPACE     |
| euckr_bin                  | euckr    |  85 |         | Yes      |       1 | PAD SPACE     |
| euckr_korean_ci            | euckr    |  19 | Yes     | Yes      |       1 | PAD SPACE     |
| gb18030_bin                | gb18030  | 249 |         | Yes      |       1 | PAD SPACE     |
| gb18030_chinese_ci         | gb18030  | 248 | Yes     | Yes      |       2 | PAD SPACE     |
| gb18030_unicode_520_ci     | gb18030  | 250 |         | Yes      |       8 | PAD SPACE     |
| gb2312_bin                 | gb2312   |  86 |         | Yes      |       1 | PAD SPACE     |
| gb2312_chinese_ci          | gb2312   |  24 | Yes     | Yes      |       1 | PAD SPACE     |
| gbk_bin                    | gbk      |  87 |         | Yes      |       1 | PAD SPACE     |
| gbk_chinese_ci             | gbk      |  28 | Yes     | Yes      |       1 | PAD SPACE     |
| geostd8_bin                | geostd8  |  93 |         | Yes      |       1 | PAD SPACE     |
| geostd8_general_ci         | geostd8  |  92 | Yes     | Yes      |       1 | PAD SPACE     |
| greek_bin                  | greek    |  70 |         | Yes      |       1 | PAD SPACE     |
| greek_general_ci           | greek    |  25 | Yes     | Yes      |       1 | PAD SPACE     |
| hebrew_bin                 | hebrew   |  71 |         | Yes      |       1 | PAD SPACE     |
| hebrew_general_ci          | hebrew   |  16 | Yes     | Yes      |       1 | PAD SPACE     |
| hp8_bin                    | hp8      |  72 |         | Yes      |       1 | PAD SPACE     |
| hp8_english_ci             | hp8      |   6 | Yes     | Yes      |       1 | PAD SPACE     |
| keybcs2_bin                | keybcs2  |  73 |         | Yes      |       1 | PAD SPACE     |
| keybcs2_general_ci         | keybcs2  |  37 | Yes     | Yes      |       1 | PAD SPACE     |
| koi8r_bin                  | koi8r    |  74 |         | Yes      |       1 | PAD SPACE     |
| koi8r_general_ci           | koi8r    |   7 | Yes     | Yes      |       1 | PAD SPACE     |
| koi8u_bin                  | koi8u    |  75 |         | Yes      |       1 | PAD SPACE     |
| koi8u_general_ci           | koi8u    |  22 | Yes     | Yes      |       1 | PAD SPACE     |
| latin1_bin                 | latin1   |  47 |         | Yes      |       1 | PAD SPACE     |
| latin1_danish_ci           | latin1   |  15 |         | Yes      |       1 | PAD SPACE     |
| latin1_general_ci          | latin1   |  48 |         | Yes      |       1 | PAD SPACE     |
| latin1_general_cs          | latin1   |  49 |         | Yes      |       1 | PAD SPACE     |
| latin1_german1_ci          | latin1   |   5 |         | Yes      |       1 | PAD SPACE     |
| latin1_german2_ci          | latin1   |  31 |         | Yes      |       2 | PAD SPACE     |
| latin1_spanish_ci          | latin1   |  94 |         | Yes      |       1 | PAD SPACE     |
| latin1_swedish_ci          | latin1   |   8 | Yes     | Yes      |       1 | PAD SPACE     |
| latin2_bin                 | latin2   |  77 |         | Yes      |       1 | PAD SPACE     |
| latin2_croatian_ci         | latin2   |  27 |         | Yes      |       1 | PAD SPACE     |
| latin2_czech_cs            | latin2   |   2 |         | Yes      |       4 | PAD SPACE     |
| latin2_general_ci          | latin2   |   9 | Yes     | Yes      |       1 | PAD SPACE     |
| latin2_hungarian_ci        | latin2   |  21 |         | Yes      |       1 | PAD SPACE     |
| latin5_bin                 | latin5   |  78 |         | Yes      |       1 | PAD SPACE     |
| latin5_turkish_ci          | latin5   |  30 | Yes     | Yes      |       1 | PAD SPACE     |
| latin7_bin                 | latin7   |  79 |         | Yes      |       1 | PAD SPACE     |
| latin7_estonian_cs         | latin7   |  20 |         | Yes      |       1 | PAD SPACE     |
| latin7_general_ci          | latin7   |  41 | Yes     | Yes      |       1 | PAD SPACE     |
| latin7_general_cs          | latin7   |  42 |         | Yes      |       1 | PAD SPACE     |
| macce_bin                  | macce    |  43 |         | Yes      |       1 | PAD SPACE     |
| macce_general_ci           | macce    |  38 | Yes     | Yes      |       1 | PAD SPACE     |
| macroman_bin               | macroman |  53 |         | Yes      |       1 | PAD SPACE     |
| macroman_general_ci        | macroman |  39 | Yes     | Yes      |       1 | PAD SPACE     |
| sjis_bin                   | sjis     |  88 |         | Yes      |       1 | PAD SPACE     |
| sjis_japanese_ci           | sjis     |  13 | Yes     | Yes      |       1 | PAD SPACE     |
| swe7_bin                   | swe7     |  82 |         | Yes      |       1 | PAD SPACE     |
| swe7_swedish_ci            | swe7     |  10 | Yes     | Yes      |       1 | PAD SPACE     |
| tis620_bin                 | tis620   |  89 |         | Yes      |       1 | PAD SPACE     |
| tis620_thai_ci             | tis620   |  18 | Yes     | Yes      |       4 | PAD SPACE     |
| ucs2_bin                   | ucs2     |  90 |         | Yes      |       1 | PAD SPACE     |
| ucs2_croatian_ci           | ucs2     | 149 |         | Yes      |       8 | PAD SPACE     |
| ucs2_czech_ci              | ucs2     | 138 |         | Yes      |       8 | PAD SPACE     |
| ucs2_danish_ci             | ucs2     | 139 |         | Yes      |       8 | PAD SPACE     |
| ucs2_esperanto_ci          | ucs2     | 145 |         | Yes      |       8 | PAD SPACE     |
| ucs2_estonian_ci           | ucs2     | 134 |         | Yes      |       8 | PAD SPACE     |
| ucs2_general_ci            | ucs2     |  35 | Yes     | Yes      |       1 | PAD SPACE     |
| ucs2_general_mysql500_ci   | ucs2     | 159 |         | Yes      |       1 | PAD SPACE     |
| ucs2_german2_ci            | ucs2     | 148 |         | Yes      |       8 | PAD SPACE     |
| ucs2_hungarian_ci          | ucs2     | 146 |         | Yes      |       8 | PAD SPACE     |
| ucs2_icelandic_ci          | ucs2     | 129 |         | Yes      |       8 | PAD SPACE     |
| ucs2_latvian_ci            | ucs2     | 130 |         | Yes      |       8 | PAD SPACE     |
| ucs2_lithuanian_ci         | ucs2     | 140 |         | Yes      |       8 | PAD SPACE     |
| ucs2_persian_ci            | ucs2     | 144 |         | Yes      |       8 | PAD SPACE     |
| ucs2_polish_ci             | ucs2     | 133 |         | Yes      |       8 | PAD SPACE     |
| ucs2_romanian_ci           | ucs2     | 131 |         | Yes      |       8 | PAD SPACE     |
| ucs2_roman_ci              | ucs2     | 143 |         | Yes      |       8 | PAD SPACE     |
| ucs2_sinhala_ci            | ucs2     | 147 |         | Yes      |       8 | PAD SPACE     |
| ucs2_slovak_ci             | ucs2     | 141 |         | Yes      |       8 | PAD SPACE     |
| ucs2_slovenian_ci          | ucs2     | 132 |         | Yes      |       8 | PAD SPACE     |
| ucs2_spanish2_ci           | ucs2     | 142 |         | Yes      |       8 | PAD SPACE     |
| ucs2_spanish_ci            | ucs2     | 135 |         | Yes      |       8 | PAD SPACE     |
| ucs2_swedish_ci            | ucs2     | 136 |         | Yes      |       8 | PAD SPACE     |
| ucs2_turkish_ci            | ucs2     | 137 |         | Yes      |       8 | PAD SPACE     |
| ucs2_unicode_520_ci        | ucs2     | 150 |         | Yes      |       8 | PAD SPACE     |
| ucs2_unicode_ci            | ucs2     | 128 |         | Yes      |       8 | PAD SPACE     |
| ucs2_vietnamese_ci         | ucs2     | 151 |         | Yes      |       8 | PAD SPACE     |
| ujis_bin                   | ujis     |  91 |         | Yes      |       1 | PAD SPACE     |
| ujis_japanese_ci           | ujis     |  12 | Yes     | Yes      |       1 | PAD SPACE     |
| utf16le_bin                | utf16le  |  62 |         | Yes      |       1 | PAD SPACE     |
| utf16le_general_ci         | utf16le  |  56 | Yes     | Yes      |       1 | PAD SPACE     |
| utf16_bin                  | utf16    |  55 |         | Yes      |       1 | PAD SPACE     |
| utf16_croatian_ci          | utf16    | 122 |         | Yes      |       8 | PAD SPACE     |
| utf16_czech_ci             | utf16    | 111 |         | Yes      |       8 | PAD SPACE     |
| utf16_danish_ci            | utf16    | 112 |         | Yes      |       8 | PAD SPACE     |
| utf16_esperanto_ci         | utf16    | 118 |         | Yes      |       8 | PAD SPACE     |
| utf16_estonian_ci          | utf16    | 107 |         | Yes      |       8 | PAD SPACE     |
| utf16_general_ci           | utf16    |  54 | Yes     | Yes      |       1 | PAD SPACE     |
| utf16_german2_ci           | utf16    | 121 |         | Yes      |       8 | PAD SPACE     |
| utf16_hungarian_ci         | utf16    | 119 |         | Yes      |       8 | PAD SPACE     |
| utf16_icelandic_ci         | utf16    | 102 |         | Yes      |       8 | PAD SPACE     |
| utf16_latvian_ci           | utf16    | 103 |         | Yes      |       8 | PAD SPACE     |
| utf16_lithuanian_ci        | utf16    | 113 |         | Yes      |       8 | PAD SPACE     |
| utf16_persian_ci           | utf16    | 117 |         | Yes      |       8 | PAD SPACE     |
| utf16_polish_ci            | utf16    | 106 |         | Yes      |       8 | PAD SPACE     |
| utf16_romanian_ci          | utf16    | 104 |         | Yes      |       8 | PAD SPACE     |
| utf16_roman_ci             | utf16    | 116 |         | Yes      |       8 | PAD SPACE     |
| utf16_sinhala_ci           | utf16    | 120 |         | Yes      |       8 | PAD SPACE     |
| utf16_slovak_ci            | utf16    | 114 |         | Yes      |       8 | PAD SPACE     |
| utf16_slovenian_ci         | utf16    | 105 |         | Yes      |       8 | PAD SPACE     |
| utf16_spanish2_ci          | utf16    | 115 |         | Yes      |       8 | PAD SPACE     |
| utf16_spanish_ci           | utf16    | 108 |         | Yes      |       8 | PAD SPACE     |
| utf16_swedish_ci           | utf16    | 109 |         | Yes      |       8 | PAD SPACE     |
| utf16_turkish_ci           | utf16    | 110 |         | Yes      |       8 | PAD SPACE     |
| utf16_unicode_520_ci       | utf16    | 123 |         | Yes      |       8 | PAD SPACE     |
| utf16_unicode_ci           | utf16    | 101 |         | Yes      |       8 | PAD SPACE     |
| utf16_vietnamese_ci        | utf16    | 124 |         | Yes      |       8 | PAD SPACE     |
| utf32_bin                  | utf32    |  61 |         | Yes      |       1 | PAD SPACE     |
| utf32_croatian_ci          | utf32    | 181 |         | Yes      |       8 | PAD SPACE     |
| utf32_czech_ci             | utf32    | 170 |         | Yes      |       8 | PAD SPACE     |
| utf32_danish_ci            | utf32    | 171 |         | Yes      |       8 | PAD SPACE     |
| utf32_esperanto_ci         | utf32    | 177 |         | Yes      |       8 | PAD SPACE     |
| utf32_estonian_ci          | utf32    | 166 |         | Yes      |       8 | PAD SPACE     |
| utf32_general_ci           | utf32    |  60 | Yes     | Yes      |       1 | PAD SPACE     |
| utf32_german2_ci           | utf32    | 180 |         | Yes      |       8 | PAD SPACE     |
| utf32_hungarian_ci         | utf32    | 178 |         | Yes      |       8 | PAD SPACE     |
| utf32_icelandic_ci         | utf32    | 161 |         | Yes      |       8 | PAD SPACE     |
| utf32_latvian_ci           | utf32    | 162 |         | Yes      |       8 | PAD SPACE     |
| utf32_lithuanian_ci        | utf32    | 172 |         | Yes      |       8 | PAD SPACE     |
| utf32_persian_ci           | utf32    | 176 |         | Yes      |       8 | PAD SPACE     |
| utf32_polish_ci            | utf32    | 165 |         | Yes      |       8 | PAD SPACE     |
| utf32_romanian_ci          | utf32    | 163 |         | Yes      |       8 | PAD SPACE     |
| utf32_roman_ci             | utf32    | 175 |         | Yes      |       8 | PAD SPACE     |
| utf32_sinhala_ci           | utf32    | 179 |         | Yes      |       8 | PAD SPACE     |
| utf32_slovak_ci            | utf32    | 173 |         | Yes      |       8 | PAD SPACE     |
| utf32_slovenian_ci         | utf32    | 164 |         | Yes      |       8 | PAD SPACE     |
| utf32_spanish2_ci          | utf32    | 174 |         | Yes      |       8 | PAD SPACE     |
| utf32_spanish_ci           | utf32    | 167 |         | Yes      |       8 | PAD SPACE     |
| utf32_swedish_ci           | utf32    | 168 |         | Yes      |       8 | PAD SPACE     |
| utf32_turkish_ci           | utf32    | 169 |         | Yes      |       8 | PAD SPACE     |
| utf32_unicode_520_ci       | utf32    | 182 |         | Yes      |       8 | PAD SPACE     |
| utf32_unicode_ci           | utf32    | 160 |         | Yes      |       8 | PAD SPACE     |
| utf32_vietnamese_ci        | utf32    | 183 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_0900_ai_ci         | utf8mb4  | 255 | Yes     | Yes      |       0 | NO PAD        |
| utf8mb4_0900_as_ci         | utf8mb4  | 305 |         | Yes      |       0 | NO PAD        |
| utf8mb4_0900_as_cs         | utf8mb4  | 278 |         | Yes      |       0 | NO PAD        |
| utf8mb4_0900_bin           | utf8mb4  | 309 |         | Yes      |       1 | NO PAD        |
| utf8mb4_bin                | utf8mb4  |  46 |         | Yes      |       1 | PAD SPACE     |
| utf8mb4_croatian_ci        | utf8mb4  | 245 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_cs_0900_ai_ci      | utf8mb4  | 266 |         | Yes      |       0 | NO PAD        |
| utf8mb4_cs_0900_as_cs      | utf8mb4  | 289 |         | Yes      |       0 | NO PAD        |
| utf8mb4_czech_ci           | utf8mb4  | 234 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_danish_ci          | utf8mb4  | 235 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_da_0900_ai_ci      | utf8mb4  | 267 |         | Yes      |       0 | NO PAD        |
| utf8mb4_da_0900_as_cs      | utf8mb4  | 290 |         | Yes      |       0 | NO PAD        |
| utf8mb4_de_pb_0900_ai_ci   | utf8mb4  | 256 |         | Yes      |       0 | NO PAD        |
| utf8mb4_de_pb_0900_as_cs   | utf8mb4  | 279 |         | Yes      |       0 | NO PAD        |
| utf8mb4_eo_0900_ai_ci      | utf8mb4  | 273 |         | Yes      |       0 | NO PAD        |
| utf8mb4_eo_0900_as_cs      | utf8mb4  | 296 |         | Yes      |       0 | NO PAD        |
| utf8mb4_esperanto_ci       | utf8mb4  | 241 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_estonian_ci        | utf8mb4  | 230 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_es_0900_ai_ci      | utf8mb4  | 263 |         | Yes      |       0 | NO PAD        |
| utf8mb4_es_0900_as_cs      | utf8mb4  | 286 |         | Yes      |       0 | NO PAD        |
| utf8mb4_es_trad_0900_ai_ci | utf8mb4  | 270 |         | Yes      |       0 | NO PAD        |
| utf8mb4_es_trad_0900_as_cs | utf8mb4  | 293 |         | Yes      |       0 | NO PAD        |
| utf8mb4_et_0900_ai_ci      | utf8mb4  | 262 |         | Yes      |       0 | NO PAD        |
| utf8mb4_et_0900_as_cs      | utf8mb4  | 285 |         | Yes      |       0 | NO PAD        |
| utf8mb4_general_ci         | utf8mb4  |  45 |         | Yes      |       1 | PAD SPACE     |
| utf8mb4_german2_ci         | utf8mb4  | 244 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_hr_0900_ai_ci      | utf8mb4  | 275 |         | Yes      |       0 | NO PAD        |
| utf8mb4_hr_0900_as_cs      | utf8mb4  | 298 |         | Yes      |       0 | NO PAD        |
| utf8mb4_hungarian_ci       | utf8mb4  | 242 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_hu_0900_ai_ci      | utf8mb4  | 274 |         | Yes      |       0 | NO PAD        |
| utf8mb4_hu_0900_as_cs      | utf8mb4  | 297 |         | Yes      |       0 | NO PAD        |
| utf8mb4_icelandic_ci       | utf8mb4  | 225 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_is_0900_ai_ci      | utf8mb4  | 257 |         | Yes      |       0 | NO PAD        |
| utf8mb4_is_0900_as_cs      | utf8mb4  | 280 |         | Yes      |       0 | NO PAD        |
| utf8mb4_ja_0900_as_cs      | utf8mb4  | 303 |         | Yes      |       0 | NO PAD        |
| utf8mb4_ja_0900_as_cs_ks   | utf8mb4  | 304 |         | Yes      |      24 | NO PAD        |
| utf8mb4_latvian_ci         | utf8mb4  | 226 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_la_0900_ai_ci      | utf8mb4  | 271 |         | Yes      |       0 | NO PAD        |
| utf8mb4_la_0900_as_cs      | utf8mb4  | 294 |         | Yes      |       0 | NO PAD        |
| utf8mb4_lithuanian_ci      | utf8mb4  | 236 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_lt_0900_ai_ci      | utf8mb4  | 268 |         | Yes      |       0 | NO PAD        |
| utf8mb4_lt_0900_as_cs      | utf8mb4  | 291 |         | Yes      |       0 | NO PAD        |
| utf8mb4_lv_0900_ai_ci      | utf8mb4  | 258 |         | Yes      |       0 | NO PAD        |
| utf8mb4_lv_0900_as_cs      | utf8mb4  | 281 |         | Yes      |       0 | NO PAD        |
| utf8mb4_persian_ci         | utf8mb4  | 240 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_pl_0900_ai_ci      | utf8mb4  | 261 |         | Yes      |       0 | NO PAD        |
| utf8mb4_pl_0900_as_cs      | utf8mb4  | 284 |         | Yes      |       0 | NO PAD        |
| utf8mb4_polish_ci          | utf8mb4  | 229 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_romanian_ci        | utf8mb4  | 227 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_roman_ci           | utf8mb4  | 239 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_ro_0900_ai_ci      | utf8mb4  | 259 |         | Yes      |       0 | NO PAD        |
| utf8mb4_ro_0900_as_cs      | utf8mb4  | 282 |         | Yes      |       0 | NO PAD        |
| utf8mb4_ru_0900_ai_ci      | utf8mb4  | 306 |         | Yes      |       0 | NO PAD        |
| utf8mb4_ru_0900_as_cs      | utf8mb4  | 307 |         | Yes      |       0 | NO PAD        |
| utf8mb4_sinhala_ci         | utf8mb4  | 243 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_sk_0900_ai_ci      | utf8mb4  | 269 |         | Yes      |       0 | NO PAD        |
| utf8mb4_sk_0900_as_cs      | utf8mb4  | 292 |         | Yes      |       0 | NO PAD        |
| utf8mb4_slovak_ci          | utf8mb4  | 237 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_slovenian_ci       | utf8mb4  | 228 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_sl_0900_ai_ci      | utf8mb4  | 260 |         | Yes      |       0 | NO PAD        |
| utf8mb4_sl_0900_as_cs      | utf8mb4  | 283 |         | Yes      |       0 | NO PAD        |
| utf8mb4_spanish2_ci        | utf8mb4  | 238 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_spanish_ci         | utf8mb4  | 231 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_sv_0900_ai_ci      | utf8mb4  | 264 |         | Yes      |       0 | NO PAD        |
| utf8mb4_sv_0900_as_cs      | utf8mb4  | 287 |         | Yes      |       0 | NO PAD        |
| utf8mb4_swedish_ci         | utf8mb4  | 232 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_tr_0900_ai_ci      | utf8mb4  | 265 |         | Yes      |       0 | NO PAD        |
| utf8mb4_tr_0900_as_cs      | utf8mb4  | 288 |         | Yes      |       0 | NO PAD        |
| utf8mb4_turkish_ci         | utf8mb4  | 233 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_unicode_520_ci     | utf8mb4  | 246 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_unicode_ci         | utf8mb4  | 224 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_vietnamese_ci      | utf8mb4  | 247 |         | Yes      |       8 | PAD SPACE     |
| utf8mb4_vi_0900_ai_ci      | utf8mb4  | 277 |         | Yes      |       0 | NO PAD        |
| utf8mb4_vi_0900_as_cs      | utf8mb4  | 300 |         | Yes      |       0 | NO PAD        |
| utf8mb4_zh_0900_as_cs      | utf8mb4  | 308 |         | Yes      |       0 | NO PAD        |
| utf8_bin                   | utf8     |  83 |         | Yes      |       1 | PAD SPACE     |
| utf8_croatian_ci           | utf8     | 213 |         | Yes      |       8 | PAD SPACE     |
| utf8_czech_ci              | utf8     | 202 |         | Yes      |       8 | PAD SPACE     |
| utf8_danish_ci             | utf8     | 203 |         | Yes      |       8 | PAD SPACE     |
| utf8_esperanto_ci          | utf8     | 209 |         | Yes      |       8 | PAD SPACE     |
| utf8_estonian_ci           | utf8     | 198 |         | Yes      |       8 | PAD SPACE     |
| utf8_general_ci            | utf8     |  33 | Yes     | Yes      |       1 | PAD SPACE     |
| utf8_general_mysql500_ci   | utf8     | 223 |         | Yes      |       1 | PAD SPACE     |
| utf8_german2_ci            | utf8     | 212 |         | Yes      |       8 | PAD SPACE     |
| utf8_hungarian_ci          | utf8     | 210 |         | Yes      |       8 | PAD SPACE     |
| utf8_icelandic_ci          | utf8     | 193 |         | Yes      |       8 | PAD SPACE     |
| utf8_latvian_ci            | utf8     | 194 |         | Yes      |       8 | PAD SPACE     |
| utf8_lithuanian_ci         | utf8     | 204 |         | Yes      |       8 | PAD SPACE     |
| utf8_persian_ci            | utf8     | 208 |         | Yes      |       8 | PAD SPACE     |
| utf8_polish_ci             | utf8     | 197 |         | Yes      |       8 | PAD SPACE     |
| utf8_romanian_ci           | utf8     | 195 |         | Yes      |       8 | PAD SPACE     |
| utf8_roman_ci              | utf8     | 207 |         | Yes      |       8 | PAD SPACE     |
| utf8_sinhala_ci            | utf8     | 211 |         | Yes      |       8 | PAD SPACE     |
| utf8_slovak_ci             | utf8     | 205 |         | Yes      |       8 | PAD SPACE     |
| utf8_slovenian_ci          | utf8     | 196 |         | Yes      |       8 | PAD SPACE     |
| utf8_spanish2_ci           | utf8     | 206 |         | Yes      |       8 | PAD SPACE     |
| utf8_spanish_ci            | utf8     | 199 |         | Yes      |       8 | PAD SPACE     |
| utf8_swedish_ci            | utf8     | 200 |         | Yes      |       8 | PAD SPACE     |
| utf8_tolower_ci            | utf8     |  76 |         | Yes      |       1 | PAD SPACE     |
| utf8_turkish_ci            | utf8     | 201 |         | Yes      |       8 | PAD SPACE     |
| utf8_unicode_520_ci        | utf8     | 214 |         | Yes      |       8 | PAD SPACE     |
| utf8_unicode_ci            | utf8     | 192 |         | Yes      |       8 | PAD SPACE     |
| utf8_vietnamese_ci         | utf8     | 215 |         | Yes      |       8 | PAD SPACE     |
+----------------------------+----------+-----+---------+----------+---------+---------------+
272 rows in set (0.00 sec)

#utf8_general_ci 不区分大小写
#utf8_bin 区分大小写

查看当前使用的排序规则

mysql> show variables like 'collation%';
+----------------------+-------------------+
| Variable_name        | Value             |
+----------------------+-------------------+
| collation_connection | latin1_swedish_ci |
| collation_database   | latin1_swedish_ci |
| collation_server     | latin1_swedish_ci |
+----------------------+-------------------+
3 rows in set (0.00 sec)

生产环境中，使用uf8mb4编码，使用默认排序规则

3.3管理数据库

3.3.1查看数据库列表

格式：

SHOW DATABASES;

范例：

#默认这四个系统库，不能删除
[root@localhost ~ 16:10:31]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

`mysql> show databases;`
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.00 sec)

3.3.2 创建数据库

格式：

mysql> help create database;
Name: 'CREATE DATABASE'
Description:
Syntax:
CREATE {DATABASE | SCHEMA} [IF NOT EXISTS] db_name
    [create_option] ...

create_option: [DEFAULT] {
    CHARACTER SET [=] charset_name
  | COLLATE [=] collation_name
  | ENCRYPTION [=] {'Y' | 'N'}
}

CREATE DATABASE creates a database with the given name. To use this
statement, you need the CREATE privilege for the database. CREATE
SCHEMA is a synonym for CREATE DATABASE.

URL: https://dev.mysql.com/doc/refman/8.0/en/create-database.html

格式：查询数据库创建语句

SHOW CREATE DATABASE DBNAME;

范例：

mysql> create database testdb1;
Query OK, 1 row affected (0.01 sec)

#如果已存在，再次创建会报错
mysql> create database testdb1;
ERROR 1007 (HY000): Can't create database 'testdb1'; database exists


#不报错，但也没有创建，if not exists表示如果不存在则创建
mysql> create database if not exists testdb1;
Query OK, 1 row affected, 1 warning (0.00 sec)

#查看数据库列表
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| testdb1            |
+--------------------+
5 rows in set (0.01 sec)

#查看创建语句，包含默认字符集
mysql> show create database testdb1;
+----------+-----------------------------------------------------------------------------------------------------------------------------------+
| Database | Create Database                                                                                                                   |
+----------+-----------------------------------------------------------------------------------------------------------------------------------+
| testdb1  | CREATE DATABASE `testdb1` /*!40100 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci */ /*!80016 DEFAULT ENCRYPTION='N' */ |
+----------+-----------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

#创建时指定字符集
mysql> create database testdb2 default character set latin1;
Query OK, 1 row affected (0.00 sec)

#查看创建语句
mysql> show create database testdb2;
+----------+-------------------------------------------------------------------------------------------------------+
| Database | Create Database                                                                                       |
+----------+-------------------------------------------------------------------------------------------------------+
| testdb2  | CREATE DATABASE `testdb2` /*!40100 DEFAULT CHARACTER SET latin1 */ /*!80016 DEFAULT ENCRYPTION='N' */ |
+----------+-------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

创建两个数据库，本质上是在硬盘上创建了两个目录

[root@localhost ~ 16:13:18]# ls -d /var/lib/mysql/testdb*
/var/lib/mysql/testdb1  /var/lib/mysql/testdb2

3.3.3 修改数据库

mysql> help alter database;
Name: 'ALTER DATABASE'
Description:
Syntax:
ALTER {DATABASE | SCHEMA} [db_name]
    alter_option ...

alter_option: {
    [DEFAULT] CHARACTER SET [=] charset_name
  | [DEFAULT] COLLATE [=] collation_name
  | [DEFAULT] ENCRYPTION [=] {'Y' | 'N'}
  | READ ONLY [=] {DEFAULT | 0 | 1}
}

ALTER DATABASE enables you to change the overall characteristics of a
database. These characteristics are stored in the data dictionary. This
statement requires the ALTER privilege on the database. ALTER SCHEMA is
a synonym for ALTER DATABASE.

If the database name is omitted, the statement applies to the default
database. In that case, an error occurs if there is no default
database.

For any alter_option omitted from the statement, the database retains
its current option value, with the exception that changing the
character set may change the collation and vice versa.

o https://dev.mysql.com/doc/refman/8.0/en/alter-database.html#alter-dat
  abase-charset

o https://dev.mysql.com/doc/refman/8.0/en/alter-database.html#alter-dat
  abase-encryption

o https://dev.mysql.com/doc/refman/8.0/en/alter-database.html#alter-dat
  abase-read-only

Character Set and Collation Options

The CHARACTER SET option changes the default database character set.
The COLLATE option changes the default database collation. For
information about character set and collation names, see
https://dev.mysql.com/doc/refman/8.0/en/charset.html.

To see the available character sets and collations, use the SHOW
CHARACTER SET and SHOW COLLATION statements, respectively. See [HELP
SHOW CHARACTER SET], and [HELP SHOW COLLATION].

A stored routine that uses the database defaults when the routine is
created includes those defaults as part of its definition. (In a stored
routine, variables with character data types use the database defaults
if the character set or collation are not specified explicitly. See
[HELP CREATE PROCEDURE].) If you change the default character set or
collation for a database, any stored routines that are to use the new
defaults must be dropped and recreated.

Encryption Option

The ENCRYPTION option, introduced in MySQL 8.0.16, defines the default
database encryption, which is inherited by tables created in the
database. The permitted values are 'Y' (encryption enabled) and 'N'
(encryption disabled). Only newly created tables inherit the default
database encryption. For existing tables associated with the database,
their encryption remains unchanged. If the
table_encryption_privilege_check system variable is enabled, the
TABLE_ENCRYPTION_ADMIN privilege is required to specify a default
encryption setting that differs from the value of the
default_table_encryption system variable. For more information, see
https://dev.mysql.com/doc/refman/8.0/en/innodb-data-encryption.html#inn
odb-schema-tablespace-encryption-default.

Read Only Option

The READ ONLY option, introduced in MySQL 8.0.22, controls whether to
permit modification of the database and objects within it. The
permitted values are DEFAULT or 0 (not read only) and 1 (read only).
This option is useful for database migration because a database for
which READ ONLY is enabled can be migrated to another MySQL instance
without concern that the database might be changed during the
operation.

With NDB Cluster, making a database read only on one mysqld server is
synchronized to other mysqld servers in the same cluster, so that the
database becomes read only on all mysqld servers.

The READ ONLY option, if enabled, is displayed in the
INFORMATION_SCHEMA SCHEMATA_EXTENSIONS table. See
https://dev.mysql.com/doc/refman/8.0/en/information-schema-schemata-ext
ensions-table.html.

The READ ONLY option cannot be enabled for these system schemas: mysql,
information_schema, performance_schema.

In ALTER DATABASE statements, the READ ONLY option interacts with other
instances of itself and with other options as follows:

o An error occurs if multiple instances of READ ONLY conflict (for
  example, READ ONLY = 1 READ ONLY = 0).

o An ALTER DATABASE statement that contains only (nonconflicting) READ
  ONLY options is permitted even for a read-only database.

o A mix of (nonconflicting) READ ONLY options with other options is
  permitted if the read-only state of the database either before or
  after the statement permits modifications. If the read-only state
  both before and after prohibits changes, an error occurs.

  This statement succeeds whether or not the database is read only:

ALTER DATABASE mydb READ ONLY = 0 DEFAULT COLLATE utf8mb4_bin;

  This statement succeeds if the database is not read only, but fails
  if it is already read only:

ALTER DATABASE mydb READ ONLY = 1 DEFAULT COLLATE utf8mb4_bin;

Enabling READ ONLY affects all users of the database, with these
exceptions that are not subject to read-only checks:

o Statements executed by the server as part of server initialization,
  restart, upgrade, or replication.

o Statements in a file named at server startup by the init_file system
  variable.

o TEMPORARY tables; it is possible to create, alter, drop, and write to
  TEMPORARY tables in a read-only database.

o NDB Cluster non-SQL inserts and updates.

Other than for the excepted operations just listed, enabling READ ONLY
prohibits write operations to the database and its objects, including
their definitions, data, and metadata. The following list details
affected SQL statements and operations:

o The database itself:

  o CREATE DATABASE

  o ALTER DATABASE (except to change the READ ONLY option)

  o DROP DATABASE

o Views:

  o CREATE VIEW

  o ALTER VIEW

  o DROP VIEW

  o Selecting from views that invoke functions with side effects.

  o Updating updatable views.

  o Statements that create or drop objects in a writable database are
    rejected if they affect metadata of a view in a read-only database
    (for example, by making the view valid or invalid).

o Stored routines:

  o CREATE PROCEDURE

  o DROP PROCEDURE

  o CALL (of procedures with side effects)

  o CREATE FUNCTION

  o DROP FUNCTION

  o SELECT (of functions with side effects)

  o For procedures and functions, read-only checks follow prelocking
    behavior. For CALL statements, read-only checks are done on a
    per-statement basis, so if some conditionally executed statement
    writing to a read-only database does not actually execute, the call
    still succeeds. On the other hand, for a function called within a
    SELECT, execution of the function body happens in prelocked mode.
    As long as a some statement within the function writes to a
    read-only database, execution of the function fails with an error
    regardless of whether the statement actually executes.

o Triggers:

  o CREATE TRIGGER

  o DROP TRIGGER

  o Trigger invocation.

o Events:

  o CREATE EVENT

  o ALTER EVENT

  o DROP EVENT

  o Event execution:

    o Executing an event in the database fails because that would
      change the last-execution timestamp, which is event metadata
      stored in the data dictionary. Failure of event execution also
      has the effect of causing the event scheduler to stop.

    o If an event writes to an object in a read-only database,
      execution of the event fails with an error, but the event
      scheduler is not stopped.

o Tables:

  o CREATE TABLE

  o ALTER TABLE

  o CREATE INDEX

  o DROP INDEX

  o RENAME TABLE

  o TRUNCATE TABLE

  o DROP TABLE

  o DELETE

  o INSERT

  o IMPORT TABLE

  o LOAD DATA

  o LOAD XML

  o REPLACE

  o UPDATE

  o For cascading foreign keys where the child table is in a read-only
    database, updates and deletes on the parent are rejected even if
    the child table is not directly affected.

  o For a MERGE table such as CREATE TABLE s1.t(i int) ENGINE MERGE
    UNION (s2.t, s3.t), INSERT_METHOD=..., the following behavior
    applies:

    o Inserting into the MERGE table (INSERT into s1.t) fails if at
      least one of s1, s2, s3 is read only, regardless of insert
      method. The insert is refused even if it would actually end up in
      a writable table.

    o Dropping the MERGE table (DROP TABLE s1.t) succeeds as long as s1
      is not read only. It is permitted to drop a MERGE table that
      refers to a read-only database.

An ALTER DATABASE statement blocks until all concurrent transactions
that have already accessed an object in the database being altered have
committed. Conversely, a write transaction accessing an object in a
database being altered in a concurrent ALTER DATABASE blocks until the
ALTER DATABASE has committed.

If the Clone plugin is used to clone a local or remote data directory,
the databases in the clone retain the read-only state they had in the
source data directory. The read-only state does not affect the cloning
process itself. If it is not desirable to have the same database
read-only state in the clone, the option must be changed explicitly for
the clone after the cloning process has finished, using ALTER DATABASE
operations on the clone.

When cloning from a donor to a recipient, if the recipient has a user
database that is read only, cloning fails with an error message.
Cloning may be retried after making the database writable.

READ ONLY is permitted for ALTER DATABASE, but not for CREATE DATABASE.
However, for a read-only database, the statement produced by SHOW
CREATE DATABASE does include READ ONLY=1 within a comment to indicate
its read-only status:
mysql> ALTER DATABASE mydb READ ONLY = 1;
mysql> SHOW CREATE DATABASE mydb\G
*************************** 1. row ***************************
       Database: mydb
Create Database: CREATE DATABASE `mydb`
                 /*!40100 DEFAULT CHARACTER SET utf8mb4
                          COLLATE utf8mb4_0900_ai_ci */
                 /*!80016 DEFAULT ENCRYPTION='N' */
                 /* READ ONLY = 1 */

If the server executes a CREATE DATABASE statement containing such a
comment, the server ignores the comment and the READ ONLY option is not
processed. This has implications for mysqldump and mysqlpump, which use
SHOW CREATE DATABASE to produce CREATE DATABASE statements in dump
output:

o In a dump file, the CREATE DATABASE statement for a read-only
  database contains the commented READ ONLY option.

o The dump file can be restored as usual, but because the server
  ignores the commented READ ONLY option, the restored database is not
  read only. If the database is to be read ony after being restored,
  you must execute ALTER DATABASE manually to make it so.

Suppose that mydb is read only and you dump it as follows:

shell> mysqldump --databases mydb > mydb.sql

A restore operation later must be followed by ALTER DATABASE if mydb
should still be read only:

shell> mysql
mysql> SOURCE mydb.sql;
mysql> ALTER DATABASE mydb READ ONLY = 1;

MySQL Enterprise Backup is not subject to this issue. It backs up and
restores a read-only database like any other, but enables the READ ONLY
option at restore time if it was enabled at backup time.

ALTER DATABASE is written to the binary log, so a change to the READ
ONLY option on a replication source server also affects replicas. To
prevent this from happening, binary logging must be disabled prior to
execution of the ALTER DATABASE statement. For example, to prepare for
migrating a database without affecting replicas, perform these
operations:

1. Within a single session, disable binary logging and enable READ ONLY
   for the database:

mysql> SET sql_log_bin = OFF;
mysql> ALTER DATABASE mydb READ ONLY = 1;

2. Dump the database, for example, with mysqldump or mysqlpump:

shell> mysqldump --databases mydb > mydb.sql

3. Within a single session, disable binary logging and disable READ
   ONLY for the database:

mysql> SET sql_log_bin = OFF;
mysql> ALTER DATABASE mydb READ ONLY = 0;

URL: https://dev.mysql.com/doc/refman/8.0/en/alter-database.html

范例：修改字符集

mysql> alter database testdb2 character set utf8mb4 collate utf8mb4_0900_ai_ci;
Query OK, 1 row affected (0.00 sec)

mysql> show create database testdb2\G
*************************** 1. row ***************************
       Database: testdb2
Create Database: CREATE DATABASE `testdb2` /*!40100 DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_0900_ai_ci */ /*!80016 DEFAULT ENCRYPTION='N' */
1 row in set (0.00 sec)

3.3.4 删除数据库

格式：

mysql> help drop database;
Name: 'DROP DATABASE'
Description:
Syntax:
DROP {DATABASE | SCHEMA} [IF EXISTS] db_name

DROP DATABASE drops all tables in the database and deletes the
database. Be very careful with this statement! To use DROP DATABASE,
you need the DROP privilege on the database. DROP SCHEMA is a synonym
for DROP DATABASE.

*Important*:

When a database is dropped, privileges granted specifically for the
database are not automatically dropped. They must be dropped manually.
See [HELP GRANT].

IF EXISTS is used to prevent an error from occurring if the database
does not exist.

URL: https://dev.mysql.com/doc/refman/8.0/en/drop-database.html

范例：

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| testdb1            |
| testdb2            |
+--------------------+
6 rows in set (0.00 sec)

#删除数据库
mysql> drop database testdb2;
Query OK, 0 rows affected (0.01 sec)

#删除不存在的库
mysql> drop database testdb2;
ERROR 1008 (HY000): Can't drop database 'testdb2'; database doesn't exist


#加if exists判断
mysql> drop database if exists testdb2;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
| testdb1            |
+--------------------+
5 rows in set (0.00 sec)

mysql> quit
Bye

#testdb2对应的目录已不存在
[root@localhost ~ 16:16:14]# ls -d /var/lib/mysql/testdb*
/var/lib/mysql/testdb1

mysqladmin命令也可以创建和删除数据库

#删除数据库testdb1
[root@localhost ~ 16:16:31]# mysqladmin drop testdb1
Dropping the database is potentially a very bad thing to do.
Any data stored in the database will be destroyed.

Do you really want to drop the 'testdb1' database [y/N] `y`
Database "testdb1" droppeddb1


[root@localhost ~ 16:16:52]# mysql -e 'show databases;'
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+

3.4数据类型

MySQL 中定义数据字段的类型对你数据库的优化是非常重要的。

MySQL 支持多种类型，大致可以分为三类：数值、日期/时间和字符串(字符)类型。

对于任何一个数据表，每一行的每一列对应的元素都是下列数据类型的一种。

类型	关键字
整数类型	TINYINT SMALLINT MEDIUMINT INT (INTEGER) BIGINT
浮点数类型	FLOAT DOUBLE
定点数类型	DECIMAL
位类型	BIT
日期时间类型	YEAR TIME DATE DATETIME TIMESTAMP
文本字符串类型	CHAR VARCHAR TINYTEXT TEXT MEDIUMTEXT LONGTEXT
枚举类型	ENUM
集合类型	SET
二进制字符串类型	BINARY VARBINARY TINYBLOB BLOB MEDIUMBLOB LONGBLOB
JSON类型	SON对象 JSON 数组
空间数据类型 (单值类型）	GEOMETRY POINT LINESTRING POLYGON
空间数据类型 (集合类型）	MULTIPOINT MULTILINESTRING MULTIPOLYGON GEOMETRYCOLLECTION

在常见数据表时，除了可以指定列的数据类型，还可以指定列的属性。

关键字	含义
NULL	数据列可包含 NULL 值
NOT NULL	数据列不允许包含 NULL 值
DEFAUTL	默认值
PRIMARY KEY	主键
AUTO_INCREMENT	自动递增，适用于整数类型
UNSIGNED	无符号
CHHARACTER SET name	指定一个字符集

3.4.1 数值型

MySQL 支持所有标准 SQL 数值数据类型。

这些类型包括严格数值数据类型(INTEGER、SMALLINT、DECIMAL 和 NUMERIC)，以及近似数值数据类型(FLOAT、REAL 和 DOUBLE PRECISION)。

关键字INT是INTEGER的同义词，关键字DEC是DECIMAL的同义词。

BIT数据类型保存位字段值，并且支持 MyISAM、MEMORY、InnoDB 和 BDB表。

作为 SQL 标准的扩展，MySQL 也支持整数类型 TINYINT、MEDIUMINT 和 BIGINT。下面的表显示了需要的每个整数类型的存储和范围。

类型	大小	范围（有符号）	范围（无符号）	用途
TINYINT	1 Bytes	(-128，127)	(0，255)	小
SMALLINT	2 Bytes	(-32 768，32 767)	(0，65 535)	大整数值
MEDIUMINT	3 Bytes	(-8 388 608，8 388 607)	(0，16 777215)	大整数值
INT或INTEGER	4 Bytes	(-2 147 483 648，2 147 483647)	(0，4 294967 295)	大整数值
BIGINT	8 Bytes	(-9 223 372 036 854 775 808，9 223 372 036 854 775807)	(0，18 446744 073 709551 615)	大整数值
FLOAT	4 Bytes	(-3.402 823 466E+38，-1.175 494 351 E-38)，0，(1.175 494 351 E-38，3.402 823 466 351E+38)	0，(1.175494 351 E-38，3.402823 466E+38)	极大整数值
DOUBLE	8 Bytes	(-1.797 693 134 862 315 7E+308，-2.225 073 858 507201 4 E-308)，0，(2.225 073858 507 201 4 E-308，1.797693 134 862 315 7 E+308)	0，(2.225073 858 507201 4 E-308，1.797693 134 862315 7 E+308)	双精度浮点数值
DECIMAL	对DECIMAL(M,D),如果M>D，为M+2否则为D+2	依赖于M和D的值	依赖于M和D的值	小数值

3.4.2 日期和时间型

表示时间值的日期和时间类型为DATETIME、DATE、TIMESTAMP、TIME和YEAR。

每个时间类型有一个有效值范围和一个"零"值，当指定不合法的MySQL不能表示的值时使用"零"值。

TIMESTAMP类型有专有的自动更新特性，将在后面描述。

类型	大小（bytes）	范围	格式	用途
DATE	3	1000-01-01/9999-12-31	YYYY-MM-DD	日期值
TIME	3	'-838:59:59'/'838:59:59'	HH:MM:SS	时间值或持续时间
YEAR	1	1901/2155	YYYY	年份值
DATETIME	8	'1000-01-01 00:00:00' 到 '9999-12-3123:59:59'	YYYY-MM-DD hh:mm:ss	混合日期和时间值
TIMESTAMP	4	'1970-01-01 00:00:01' UTC 到 '2038-01-19 03:14:07' UTC结束时间是第2147483647 秒，北京时间 2038-1-1911:14:07，格林尼治时间 2038年1月19日 凌晨 03:14:07	YYYY-MM-DD hh:mm:ss	混合日期和时间值，时间戳

3.4.3 字符串类型

字符串类型指CHAR、VARCHAR、BINARY、VARBINARY、BLOB、TEXT、ENUM和SET。该节描述了这些类型如何工作以及如何在查询中使用这些类型。

类型	大小	用途
CHAR	0-255 bytes	定长字符串
VARCHAR	0-65535 bytes	变长字符串
TINYBLOB	0-255 bytes	不超过 255 个字符的二进制字符串
TINYTEXT	0-255 bytes	短文本字符串
BLOB	0-65535 bytes	二进制形式的长文本数据
TEXT	0-65535 bytes	长文本数据
MEDIUMBLOB	0-16777215 bytes	二进制形式的中等长度文本数据
MEDIUMTEXT	0-16777215 bytes	中等长度文本数据
LONGBLOB	0-4294967295 bytes	二进制形式的极大文本数据
LONGTEXT	0-4294967295 bytes	极大文本数据

注意：char(n) 和 varchar(n) 中括号中 n 代表字符的个数，并不代表字节个数，比如 CHAR(30) 就可以存

储 30 个字符。

CHAR 和 VARCHAR 类型类似，但它们保存和检索的方式不同。它们的最大长度和是否尾部空格被保留等方面也不同。在存储或检索过程中不进行大小写转换。

BINARY 和 VARBINARY 类似于 CHAR 和 VARCHAR，不同的是它们包含二进制字符串而不要非二进制字符串。也就是说，它们包含字节字符串而不是字符字符串。这说明它们没有字符集，并且排序和比较基于列值字节的数值值。

BLOB 是一个二进制大对象，可以容纳可变数量的数据。有 4 种 BLOB 类型：TINYBLOB、BLOB、MEDIUMBLOB 和 LONGBLOB。它们区别在于可容纳存储范围不同。

有 4 种 TEXT 类型：TINYTEXT、TEXT,MEDIUMTEXT 和 LONGTEXT。对应的这 4 种 BLOB 类型，可存储的最大长度不同，可根据实际情况选择。

3.5 DDL 语句

DDL语句主要用来操作数据库中的表。

同一个库中不同表可以使用不同的存储引擎，但建议使用同一种存储引擎。

3.5.1 创建表

格式

#帮助
[root@localhost ~ 09:31:24]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> help create table;
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    (create_definition,...)
    [table_options]
    [partition_options]

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    [(create_definition,...)]
    [table_options]
    [partition_options]
    [IGNORE | REPLACE]
    [AS] query_expression

CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
    { LIKE old_tbl_name | (LIKE old_tbl_name) }

create_definition: {
    col_name column_definition
  | {INDEX | KEY} [index_name] [index_type] (key_part,...)
      [index_option] ...
  | {FULLTEXT | SPATIAL} [INDEX | KEY] [index_name] (key_part,...)
      [index_option] ...
  | [CONSTRAINT [symbol]] PRIMARY KEY
      [index_type] (key_part,...)
      [index_option] ...
  | [CONSTRAINT [symbol]] UNIQUE [INDEX | KEY]
      [index_name] [index_type] (key_part,...)
      [index_option] ...
  | [CONSTRAINT [symbol]] FOREIGN KEY
      [index_name] (col_name,...)
      reference_definition
  | check_constraint_definition
}

column_definition: {
    data_type [NOT NULL | NULL] [DEFAULT {literal | (expr)} ]
      [VISIBLE | INVISIBLE]
      [AUTO_INCREMENT] [UNIQUE [KEY]] [[PRIMARY] KEY]
      [COMMENT 'string']
      [COLLATE collation_name]
      [COLUMN_FORMAT {FIXED | DYNAMIC | DEFAULT}]
      [ENGINE_ATTRIBUTE [=] 'string']
      [SECONDARY_ENGINE_ATTRIBUTE [=] 'string']
      [STORAGE {DISK | MEMORY}]
      [reference_definition]
      [check_constraint_definition]
  | data_type
      [COLLATE collation_name]
      [GENERATED ALWAYS] AS (expr)
      [VIRTUAL | STORED] [NOT NULL | NULL]
      [VISIBLE | INVISIBLE]
      [UNIQUE [KEY]] [[PRIMARY] KEY]
      [COMMENT 'string']
      [reference_definition]
      [check_constraint_definition]
}

data_type:
    (see https://dev.mysql.com/doc/refman/8.0/en/data-types.html)

key_part: {col_name [(length)] | (expr)} [ASC | DESC]

index_type:
    USING {BTREE | HASH}

index_option: {
    KEY_BLOCK_SIZE [=] value
  | index_type
  | WITH PARSER parser_name
  | COMMENT 'string'
  | {VISIBLE | INVISIBLE}
  |ENGINE_ATTRIBUTE [=] 'string'
  |SECONDARY_ENGINE_ATTRIBUTE [=] 'string'
}

check_constraint_definition:
    [CONSTRAINT [symbol]] CHECK (expr) [[NOT] ENFORCED]

reference_definition:
    REFERENCES tbl_name (key_part,...)
      [MATCH FULL | MATCH PARTIAL | MATCH SIMPLE]
      [ON DELETE reference_option]
      [ON UPDATE reference_option]

reference_option:
    RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT

table_options:
    table_option [[,] table_option] ...

table_option: {
    AUTOEXTEND_SIZE [=] value
  | AUTO_INCREMENT [=] value
  | AVG_ROW_LENGTH [=] value
  | [DEFAULT] CHARACTER SET [=] charset_name
  | CHECKSUM [=] {0 | 1}
  | [DEFAULT] COLLATE [=] collation_name
  | COMMENT [=] 'string'
  | COMPRESSION [=] {'ZLIB' | 'LZ4' | 'NONE'}
  | CONNECTION [=] 'connect_string'
  | {DATA | INDEX} DIRECTORY [=] 'absolute path to directory'
  | DELAY_KEY_WRITE [=] {0 | 1}
  | ENCRYPTION [=] {'Y' | 'N'}
  | ENGINE [=] engine_name
  | ENGINE_ATTRIBUTE [=] 'string'
  | INSERT_METHOD [=] { NO | FIRST | LAST }
  | KEY_BLOCK_SIZE [=] value
  | MAX_ROWS [=] value
  | MIN_ROWS [=] value
  | PACK_KEYS [=] {0 | 1 | DEFAULT}
  | PASSWORD [=] 'string'
  | ROW_FORMAT [=] {DEFAULT | DYNAMIC | FIXED | COMPRESSED | REDUNDANT | COMPACT}
  | SECONDARY_ENGINE_ATTRIBUTE [=] 'string'
  | STATS_AUTO_RECALC [=] {DEFAULT | 0 | 1}
  | STATS_PERSISTENT [=] {DEFAULT | 0 | 1}
  | STATS_SAMPLE_PAGES [=] value
  | TABLESPACE tablespace_name [STORAGE {DISK | MEMORY}]
  | UNION [=] (tbl_name[,tbl_name]...)
}

partition_options:
    PARTITION BY
        { [LINEAR] HASH(expr)
        | [LINEAR] KEY [ALGORITHM={1 | 2}] (column_list)
        | RANGE{(expr) | COLUMNS(column_list)}
        | LIST{(expr) | COLUMNS(column_list)} }
    [PARTITIONS num]
    [SUBPARTITION BY
        { [LINEAR] HASH(expr)
        | [LINEAR] KEY [ALGORITHM={1 | 2}] (column_list) }
      [SUBPARTITIONS num]
    ]
    [(partition_definition [, partition_definition] ...)]

partition_definition:
    PARTITION partition_name
        [VALUES
            {LESS THAN {(expr | value_list) | MAXVALUE}
            |
            IN (value_list)}]
        [[STORAGE] ENGINE [=] engine_name]
        [COMMENT [=] 'string' ]
        [DATA DIRECTORY [=] 'data_dir']
        [INDEX DIRECTORY [=] 'index_dir']
        [MAX_ROWS [=] max_number_of_rows]
        [MIN_ROWS [=] min_number_of_rows]
        [TABLESPACE [=] tablespace_name]
        [(subpartition_definition [, subpartition_definition] ...)]

subpartition_definition:
    SUBPARTITION logical_name
        [[STORAGE] ENGINE [=] engine_name]
        [COMMENT [=] 'string' ]
        [DATA DIRECTORY [=] 'data_dir']
        [INDEX DIRECTORY [=] 'index_dir']
        [MAX_ROWS [=] max_number_of_rows]
        [MIN_ROWS [=] min_number_of_rows]
        [TABLESPACE [=] tablespace_name]

query_expression:
    SELECT ...   (Some valid select or union statement)

CREATE TABLE creates a table with the given name. You must have the
CREATE privilege for the table.

By default, tables are created in the default database, using the
InnoDB storage engine. An error occurs if the table exists, if there is
no default database, or if the database does not exist.

MySQL has no limit on the number of tables. The underlying file system
may have a limit on the number of files that represent tables.
Individual storage engines may impose engine-specific constraints.
InnoDB permits up to 4 billion tables.

For information about the physical representation of a table, see
https://dev.mysql.com/doc/refman/8.0/en/create-table-files.html.

URL: https://dev.mysql.com/doc/refman/8.0/en/create-table.html

直接创建

CREATE TABLE [IF NOT EXISTS] 'tbl_name' (col1 type1 修饰符,col2 type2 修饰符,...)

#字段格式
col type1 #定义字段数据类型
PRIMARY KEY(col1,...) #将该字段设为主键
INDEX(col1,...) #设置为索引
UNIQUE KEY(COL1,...) #设置为联合主键

#表选项
ENGINE [=] engine_name
ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT}

范例

#选择数据库
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| db1                |
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
5 rows in set (0.00 sec)

mysql> use db1;
Database changed

#执行SQL语句
mysql> create table student( id int unsigned auto_increment primary key, name varchar(20) not null, age tinyint unsigned, gender enum('M','F') default 'M' )engine=innoDB auto_increment=10 default charset=utf8mb4;
Query OK, 0 rows affected (0.02 sec)

#查看
mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| student       |
+---------------+
1 row in set (0.00 sec)

#查看结构
mysql> desc student;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

#插入一条数据
mysql> insert student (name,age)values('xiaoming',20);
Query OK, 1 row affected (0.02 sec)

#查询表中的所有数据
mysql> select * from student;
+----+----------+------+--------+
| id | name     | age  | gender |
+----+----------+------+--------+
| 10 | xiaoming |   20 | M      |
+----+----------+------+--------+
1 row in set (0.00 sec)

#再次插入一条数据
mysql> insert student(name,age,gender)values('xiaohong',18,'F');
Query OK, 1 row affected (0.00 sec)

mysql> select * from student;
+----+----------+------+--------+
| id | name     | age  | gender |
+----+----------+------+--------+
| 10 | xiaoming |   20 | M      |
| 11 | xiaohong |   18 | F      |
+----+----------+------+--------+
2 rows in set (0.00 sec)

通过查询现存表创建，新表会被直接插入查询而来的数据

范例

mysql> desc student;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

#查询其他表创建
mysql> create table student2 select name,age from student;
Query OK, 2 rows affected (0.01 sec)
Records: 2  Duplicates: 0  Warnings: 0

#查看
mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| student       |
| student2      |
+---------------+
2 rows in set (0.00 sec)

#查看结构
mysql> desc student2;
+-------+------------------+------+-----+---------+-------+
| Field | Type             | Null | Key | Default | Extra |
+-------+------------------+------+-----+---------+-------+
| name  | varchar(20)      | NO   |     | NULL    |       |
| age   | tinyint unsigned | YES  |     | NULL    |       |
+-------+------------------+------+-----+---------+-------+
2 rows in set (0.00 sec)

#数据也复制过来了
mysql> select * from student2;
+----------+------+
| name     | age  |
+----------+------+
| xiaoming |   20 |
| xiaohong |   18 |
+----------+------+
2 rows in set (0.00 sec)

通过复制现存的表的表结构创建，但不复制数据

范例

mysql> desc student;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> create table student3 like student;
Query OK, 0 rows affected (0.02 sec)

mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| student       |
| student2      |
| student3      |
+---------------+
3 rows in set (0.01 sec)

mysql> desc student3;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> select * from student3;
Empty set (0.00 sec)

3.5.2 查看表

格式

mysql> help show tables;
Name: 'SHOW TABLES'
Description:
Syntax:
SHOW [EXTENDED] [FULL] TABLES
    [{FROM | IN} db_name]
    [LIKE 'pattern' | WHERE expr]

SHOW TABLES lists the non-TEMPORARY tables in a given database. You can
also get this list using the mysqlshow db_name command. The LIKE
clause, if present, indicates which table names to match. The WHERE
clause can be given to select rows using more general conditions, as
discussed in
https://dev.mysql.com/doc/refman/8.0/en/extended-show.html.

Matching performed by the LIKE clause is dependent on the setting of
the lower_case_table_names system variable.

The optional EXTENDED modifier causes SHOW TABLES to list hidden tables
created by failed ALTER TABLE statements. These temporary tables have
names beginning with #sql and can be dropped using DROP TABLE.

This statement also lists any views in the database. The optional FULL
modifier causes SHOW TABLES to display a second output column with
values of BASE TABLE for a table, VIEW for a view, or SYSTEM VIEW for
an INFORMATION_SCHEMA table.

If you have no privileges for a base table or view, it does not show up
in the output from SHOW TABLES or mysqlshow db_name.

URL: https://dev.mysql.com/doc/refman/8.0/en/show-tables.html

列出数据库中的表

格式

SHOW TABLES [FROM db_name]

范例

#查看当前库中所有表
mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| student       |
| student2      |
| student3      |
+---------------+
3 rows in set (0.00 sec)

#查看指定库中的表
mysql> show tables from db1;
+---------------+
| Tables_in_db1 |
+---------------+
| student       |
| student2      |
| student3      |
+---------------+
3 rows in set (0.00 sec)

查看建表语句

格式

SHOW CREATE TABLE [db_name.]tbl_name

范例

mysql> show create table student;
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table   | Create Table                                                                                                                                                                                                                                                                                |
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| student | CREATE TABLE `student` (
  `id` int unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL,
  `age` tinyint unsigned DEFAULT NULL,
  `gender` enum('M','F') DEFAULT 'M',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci |
+---------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

#查看指定数据库的数据表
mysql> show create table db1.student\G
*************************** 1. row ***************************
       Table: student
Create Table: CREATE TABLE `student` (
  `id` int unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(20) NOT NULL,
  `age` tinyint unsigned DEFAULT NULL,
  `gender` enum('M','F') DEFAULT 'M',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci
1 row in set (0.00 sec)

查看表结构

格式

DESC [db_name.]tbl_name
SHOW COLUMNS FROM [db_name.]tbl_name

范例

mysql> desc student;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

mysql> show columns from student;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

查看表状态

格式

SHOW TABLE STATUS LIKE 'tbl_name'

范例

mysql> show table status like 'student';
+---------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| Name    | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time         | Update_time         | Check_time | Collation          | Checksum | Create_options | Comment |
+---------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
| student | InnoDB |      10 | Dynamic    |    2 |           8192 |       16384 |               0 |            0 |         0 |             12 | 2025-12-05 09:35:45 | 2025-12-05 09:37:18 | NULL       | utf8mb4_0900_ai_ci |     NULL |                |         |
+---------+--------+---------+------------+------+----------------+-------------+-----------------+--------------+-----------+----------------+---------------------+---------------------+------------+--------------------+----------+----------------+---------+
1 row in set (0.01 sec)

mysql> show table status like 'student'\G
*************************** 1. row ***************************
           Name: student
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 2
 Avg_row_length: 8192
    Data_length: 16384
Max_data_length: 0
   Index_length: 0
      Data_free: 0
 Auto_increment: 12
    Create_time: 2025-12-05 09:35:45
    Update_time: 2025-12-05 09:37:18
     Check_time: NULL
      Collation: utf8mb4_0900_ai_ci
       Checksum: NULL
 Create_options:
        Comment:
1 row in set (0.00 sec)

#不能有库名
mysql> show table status like 'db1.student'\G
Empty set (0.00 sec)

查看库中所有表状态

格式

SHOW TABLE STATUS FROM db_name

范例

mysql> show table status from db1\G
*************************** 1. row ***************************
           Name: student
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 2
 Avg_row_length: 8192
    Data_length: 16384
Max_data_length: 0
   Index_length: 0
      Data_free: 0
 Auto_increment: 12
    Create_time: 2025-12-05 09:35:45
    Update_time: 2025-12-05 09:37:18
     Check_time: NULL
      Collation: utf8mb4_0900_ai_ci
       Checksum: NULL
 Create_options:
        Comment:
*************************** 2. row ***************************
           Name: student2
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 2
 Avg_row_length: 8192
    Data_length: 16384
Max_data_length: 0
   Index_length: 0
      Data_free: 0
 Auto_increment: NULL
    Create_time: 2025-12-05 09:38:05
    Update_time: 2025-12-05 09:38:05
     Check_time: NULL
      Collation: utf8mb4_0900_ai_ci
       Checksum: NULL
 Create_options:
        Comment:
*************************** 3. row ***************************
           Name: student3
         Engine: InnoDB
        Version: 10
     Row_format: Dynamic
           Rows: 0
 Avg_row_length: 0
    Data_length: 16384
Max_data_length: 0
   Index_length: 0
      Data_free: 0
 Auto_increment: 1
    Create_time: 2025-12-05 09:39:05
    Update_time: NULL
     Check_time: NULL
      Collation: utf8mb4_0900_ai_ci
       Checksum: NULL
 Create_options:
        Comment:
3 rows in set (0.01 sec)

查看当前MySQL服务支持的引擎

格式

SHOW ENGINES

范例

mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine             | Support | Comment                                                        | Transactions | XA   | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| FEDERATED          | NO      | Federated MySQL storage engine                                 | NULL         | NULL | NULL       |
| MEMORY             | YES     | Hash based, stored in memory, useful for temporary tables      | NO           | NO   | NO         |
| InnoDB             | DEFAULT | Supports transactions, row-level locking, and foreign keys     | YES          | YES  | YES        |
| PERFORMANCE_SCHEMA | YES     | Performance Schema                                             | NO           | NO   | NO         |
| MyISAM             | YES     | MyISAM storage engine                                          | NO           | NO   | NO         |
| MRG_MYISAM         | YES     | Collection of identical MyISAM tables                          | NO           | NO   | NO         |
| BLACKHOLE          | YES     | /dev/null storage engine (anything you write to it disappears) | NO           | NO   | NO         |
| CSV                | YES     | CSV storage engine                                             | NO           | NO   | NO         |
| ARCHIVE            | YES     | Archive storage engine                                         | NO           | NO   | NO         |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)

mysql> show engines\G
*************************** 1. row ***************************
      Engine: FEDERATED
     Support: NO
     Comment: Federated MySQL storage engine
Transactions: NULL
          XA: NULL
  Savepoints: NULL
*************************** 2. row ***************************
      Engine: MEMORY
     Support: YES
     Comment: Hash based, stored in memory, useful for temporary tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 3. row ***************************
      Engine: InnoDB
     Support: DEFAULT
     Comment: Supports transactions, row-level locking, and foreign keys
Transactions: YES
          XA: YES
  Savepoints: YES
*************************** 4. row ***************************
      Engine: PERFORMANCE_SCHEMA
     Support: YES
     Comment: Performance Schema
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 5. row ***************************
      Engine: MyISAM
     Support: YES
     Comment: MyISAM storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 6. row ***************************
      Engine: MRG_MYISAM
     Support: YES
     Comment: Collection of identical MyISAM tables
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 7. row ***************************
      Engine: BLACKHOLE
     Support: YES
     Comment: /dev/null storage engine (anything you write to it disappears)
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 8. row ***************************
      Engine: CSV
     Support: YES
     Comment: CSV storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
*************************** 9. row ***************************
      Engine: ARCHIVE
     Support: YES
     Comment: Archive storage engine
Transactions: NO
          XA: NO
  Savepoints: NO
9 rows in set (0.00 sec)

3.5.3 修改和删除表

ALTER TABLE tbl_name
[alter_option [, alter_option] ...]
[partition_options]

{ ADD COLUMN <列名> <类型>
| CHANGE COLUMN <旧列名> <新列名> <新列类型>
| ALTER COLUMN <列名> { SET DEFAULT <默认值>丨DROP DEFAULT }
| MODIFY COLUMN <列名> <类型>
| DROP COLUMN <列名>
| RENAME TO <新表名> }

范例

#修改表名
mysql> alter table student rename stu;
Query OK, 0 rows affected (0.00 sec)

mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| `stu`           |
| student2      |
| student3      |
+---------------+
3 rows in set (0.00 sec)

mysql> desc stu;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)

#添加表字段
mysql> alter table stu add phone varchar(11) after name;
Query OK, 0 rows affected (0.02 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc stu;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
`| phone  | varchar(11)      | YES  |     | NULL    |                |`
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

#修改字段类型
mysql> alter table stu modify phone int;
Query OK, 2 rows affected (0.02 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> desc stu;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| phone  |` int `             | YES  |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

#修改字段名称和类型
mysql> alter table stu change column phone mobile char(11);
Query OK, 2 rows affected (0.02 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> desc stu;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
`| mobile | char(11)         | YES  |     | NULL    |                |`
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

#删除字段
mysql> alter table stu drop column mobile;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc stu;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | varchar(20)      | NO   |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
+--------+------------------+------+-----+---------+----------------+
4 rows in set (0.01 sec)

#修改表字符集
mysql> alter table stu character set utf8;
Query OK, 0 rows affected, 1 warning (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 1

#同时修改数据类型和字符集，只修改字符集，类型也不能少
mysql> alter table stu change name name char(30) character set utf8;
Query OK, 2 rows affected, 1 warning (0.01 sec)
Records: 2  Duplicates: 0  Warnings: 1

#设置字段默认值
mysql> alter table stu alter column gender set default 'M';
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

#添加字段和修改字段
mysql> alter table stu add is_del bool default false;
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc stu;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | char(30)         | YES  |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
`| is_del | tinyint(1)       | YES  |     | 0       |                |`
+--------+------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

mysql> alter table stu add is_del bool default true;
ERROR 1060 (42S21): Duplicate column name 'is_del'
mysql> alter table stu modify is_del bool default true;
Query OK, 0 rows affected (0.00 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc stu;
+--------+------------------+------+-----+---------+----------------+
| Field  | Type             | Null | Key | Default | Extra          |
+--------+------------------+------+-----+---------+----------------+
| id     | int unsigned     | NO   | PRI | NULL    | auto_increment |
| name   | char(30)         | YES  |     | NULL    |                |
| age    | tinyint unsigned | YES  |     | NULL    |                |
| gender | enum('M','F')    | YES  |     | M       |                |
| is_del | tinyint(1)       | YES  |     `| 1       |`                |
+--------+------------------+------+-----+---------+----------------+
5 rows in set (0.00 sec)

范例

mysql> create table stu2 select * from stu;
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> desc stu2;
+--------+------------------+------+-----+---------+-------+
| Field  | Type             | Null | Key | Default | Extra |
+--------+------------------+------+-----+---------+-------+
| id     | int unsigned     | NO   |     | 0       |       |
| name   | char(30)         | YES  |     | NULL    |       |
| age    | tinyint unsigned | YES  |     | NULL    |       |
| gender | enum('M','F')    | YES  |     | M       |       |
| is_del | tinyint(1)       | YES  |     | 1       |       |
+--------+------------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

#添加主键
mysql> alter table stu2 add primary key (id);
Query OK, 0 rows affected (0.01 sec)
Records: 0  Duplicates: 0  Warnings: 0

mysql> desc stu2;
+--------+------------------+------+-----+---------+-------+
| Field  | Type             | Null | Key | Default | Extra |
+--------+------------------+------+-----+---------+-------+
| id     | int unsigned     | NO   `| PRI |` 0       |       |
| name   | char(30)         | YES  |     | NULL    |       |
| age    | tinyint unsigned | YES  |     | NULL    |       |
| gender | enum('M','F')    | YES  |     | M       |       |
| is_del | tinyint(1)       | YES  |     | 1       |       |
+--------+------------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

#删除主键
mysql> alter table stu2 drop primary key;
Query OK, 2 rows affected (0.02 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> desc stu2;
+--------+------------------+------+-----+---------+-------+
| Field  | Type             | Null | Key | Default | Extra |
+--------+------------------+------+-----+---------+-------+
| id     | int unsigned     | NO   `|     |` 0       |       |
| name   | char(30)         | YES  |     | NULL    |       |
| age    | tinyint unsigned | YES  |     | NULL    |       |
| gender | enum('M','F')    | YES  |     | M       |       |
| is_del | tinyint(1)       | YES  |     | 1       |       |
+--------+------------------+------+-----+---------+-------+
5 rows in set (0.00 sec)

删除表

格式

DROP [TEMPORARY] TABLE [IF EXISTS]
tbl_name [, tbl_name] ...
[RESTRICT | CASCADE]

范例

mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| stu           |
| stu2          |
| student2      |
| student3      |
+---------------+
4 rows in set (0.00 sec)


mysql> drop table student2;drop table db1.student3;
Query OK, 0 rows affected (0.01 sec)
Query OK, 0 rows affected (0.00 sec)

mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| stu           |
| stu2          |
+---------------+
2 rows in set (0.00 sec)

3.6 DML 语句

DML语句包括INSERT，UDPATE，DELETE

3.6.1 插入数据

INSERT可以一次往表中插入一条或多条记录

格式

mysql> help insert;
Name: 'INSERT'
Description:
Syntax:
INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name [, partition_name] ...)]
    [(col_name [, col_name] ...)]
    { {VALUES | VALUE} (value_list) [, (value_list)] ...
      |
      VALUES row_constructor_list
    }
    [AS row_alias[(col_alias [, col_alias] ...)]]
    [ON DUPLICATE KEY UPDATE assignment_list]

INSERT [LOW_PRIORITY | DELAYED | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name [, partition_name] ...)]
    [AS row_alias[(col_alias [, col_alias] ...)]]
    SET assignment_list
    [ON DUPLICATE KEY UPDATE assignment_list]

INSERT [LOW_PRIORITY | HIGH_PRIORITY] [IGNORE]
    [INTO] tbl_name
    [PARTITION (partition_name [, partition_name] ...)]
    [(col_name [, col_name] ...)]
    [AS row_alias[(col_alias [, col_alias] ...)]]
    {SELECT ... | TABLE table_name}
    [ON DUPLICATE KEY UPDATE assignment_list]

value:
    {expr | DEFAULT}

value_list:
    value [, value] ...

row_constructor_list:
    ROW(value_list)[, ROW(value_list)][, ...]

assignment:
    col_name = [row_alias.]value

assignment_list:
    assignment [, assignment] ...

INSERT inserts new rows into an existing table. The INSERT ... VALUES,
INSERT ... VALUES ROW(), and INSERT ... SET forms of the statement
insert rows based on explicitly specified values. The INSERT ... SELECT
form inserts rows selected from another table or tables. You can also
use INSERT ... TABLE in MySQL 8.0.19 and later to insert rows from a
single table. INSERT with an ON DUPLICATE KEY UPDATE clause enables
existing rows to be updated if a row to be inserted would cause a
duplicate value in a UNIQUE index or PRIMARY KEY. In MySQL 8.0.19 and
later, a row alias with one or more optional column alises can be used
with ON DUPLICATE KEY UPDATE to refer to the row to be inserted.

For additional information about INSERT ... SELECT and INSERT ... ON
DUPLICATE KEY UPDATE, see [HELP INSERT SELECT], and
https://dev.mysql.com/doc/refman/8.0/en/insert-on-duplicate.html.

In MySQL 8.0, the DELAYED keyword is accepted but ignored by the
server. For the reasons for this, see [HELP INSERT DELAYED],

Inserting into a table requires the INSERT privilege for the table. If
the ON DUPLICATE KEY UPDATE clause is used and a duplicate key causes
an UPDATE to be performed instead, the statement requires the UPDATE
privilege for the columns to be updated. For columns that are read but
not modified you need only the SELECT privilege (such as for a column
referenced only on the right hand side of an col_name=expr assignment
in an ON DUPLICATE KEY UPDATE clause).

When inserting into a partitioned table, you can control which
partitions and subpartitions accept new rows. The PARTITION clause
takes a list of the comma-separated names of one or more partitions or
subpartitions (or both) of the table. If any of the rows to be inserted
by a given INSERT statement do not match one of the partitions listed,
the INSERT statement fails with the error Found a row not matching the
given partition set. For more information and examples, see
https://dev.mysql.com/doc/refman/8.0/en/partitioning-selection.html.

URL: https://dev.mysql.com/doc/refman/8.0/en/insert.html

简化格式

INSERT tbl_name [(col1,...)] VALUES (val1,...),(val21,...)

范例

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   20 | M      |      0 |
| 11 | xiaohong |   18 | F      |      0 |
+----+----------+------+--------+--------+
2 rows in set (0.00 sec)

#给出所有字段值(给出所有字段值，可以不用标明字段，只要顺序一一对应即可)
mysql> INSERT INTO stu values(12,'xiaoli',19,'F',0);
Query OK, 1 row affected (0.01 sec)

#只给出部分字段值，因为有些字段值有默认值
mysql> insert into stu(name,age)values('xiaozhou',20);
Query OK, 1 row affected (0.00 sec)

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   20 | M      |      0 |
| 11 | xiaohong |   18 | F      |      0 |
| 12 | xiaoli   |   19 | F      |      0 |
`| 13 | xiaozhou |   20 | M      |      1 |`
+----+----------+------+--------+--------+
4 rows in set (0.00 sec)

#一次插入多条
mysql> insert into stu (name,age)values('test1',20),('test2',21),('test3',22);
Query OK, 3 rows affected (0.01 sec)
Records: 3  Duplicates: 0  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   20 | M      |      0 |
| 11 | xiaohong |   18 | F      |      0 |
| 12 | xiaoli   |   19 | F      |      0 |
| 13 | xiaozhou |   20 | M      |      1 |
`| 14 | test1    |   20 | M      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   22 | M      |      1 |`
+----+----------+------+--------+--------+
7 rows in set (0.00 sec)

#有默认值的用默认值，没有默认值的用NULL值
mysql> insert stu (age,is_del)values(23,0);
Query OK, 1 row affected (0.00 sec)

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   20 | M      |      0 |
| 11 | xiaohong |   18 | F      |      0 |
| 12 | xiaoli   |   19 | F      |      0 |
| 13 | xiaozhou |   20 | M      |      1 |
| 14 | test1    |   20 | M      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   22 | M      |      1 |
`| 17 | NULL     |   23 | M      |      0 |`
+----+----------+------+--------+--------+
8 rows in set (0.00 sec)

#如果记录不存在就新增，如果存在就更新
mysql> select * from stu where id=12;
+----+--------+------+--------+--------+
| id | name   | age  | gender | is_del |
+----+--------+------+--------+--------+
| 12 | xiaoli |   19 | F      |      0 |
+----+--------+------+--------+--------+
1 row in set (0.00 sec)

mysql> insert into stu (id,name)values(12,'zhangsan') on duplicate key update name='zhangsan';
Query OK, 2 rows affected (0.01 sec)

mysql> select * from stu where id=12;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 12 | zhangsan |   19 | F      |      0 |
+----+----------+------+--------+--------+
1 row in set (0.00 sec)

#将查询结果当值插入
mysql> insert into stu (name,age,gender) select name,age,gender from stu where id=11;
Query OK, 1 row affected (0.00 sec)
Records: 1  Duplicates: 0  Warnings: 0

mysql> select * from stu ;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   20 | M      |      0 |
`| 11 | xiaohong |   18 | F      |      0 |`
| 12 | zhangsan |   19 | F      |      0 |
| 13 | xiaozhou |   20 | M      |      1 |
| 14 | test1    |   20 | M      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   22 | M      |      1 |
| 17 | NULL     |   23 | M      |      0 |
`| 18 | xiaohong |   18 | F      |      1 |`
+----+----------+------+--------+--------+
9 rows in set (0.00 sec)

mysql> insert into stu (name,age,gender) select name,age,gender from stu where id in (11,12);
Query OK, 2 rows affected (0.00 sec)
Records: 2  Duplicates: 0  Warnings: 0

mysql> select * from stu ;                                                              +----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   20 | M      |      0 |
`| 11 | xiaohong |   18 | F      |      0 |
| 12 | zhangsan |   19 | F      |      0 |`
| 13 | xiaozhou |   20 | M      |      1 |
| 14 | test1    |   20 | M      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   22 | M      |      1 |
| 17 | NULL     |   23 | M      |      0 |
| 18 | xiaohong |   18 | F      |      1 |
`| 19 | xiaohong |   18 | F      |      1 |
| 20 | zhangsan |   19 | F      |      1 |`
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

3.6.2 更新数据

更新数据一定要加条件限制，没有条件则会更新表中所有记录。

UPDATE [LOW_PRIORITY] [IGNORE] table_reference
SET assignment_list
[WHERE where_condition]
[ORDER BY ...]
[LIMIT row_count]

范例

#不加条件表示更新所有
mysql> update stu set age=30,gender='F';
Query OK, 11 rows affected (0.00 sec)
Rows matched: 11  Changed: 11  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   30 | F      |      1 |
| 16 | test3    |   30 | F      |      1 |
| 17 | NULL     |   30 | F      |      0 |
| 18 | xiaohong |   30 | F      |      1 |
| 19 | xiaohong |   30 | F      |      1 |
| 20 | zhangsan |   30 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

#根据条件更新
mysql> update stu set age=31 where id>15;
Query OK, 5 rows affected (0.00 sec)
Rows matched: 5  Changed: 5  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   30 | F      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   31 | F      |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

#多个条件，满足任何一个条件都更新 OR 可以写成 ||
mysql> update stu set age=21,gender='M' where (id=15 or name is null);
Query OK, 2 rows affected (0.00 sec)
Rows matched: 2  Changed: 2  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
`| 15 | test2    |   21 | M      |      1 |`
| 16 | test3    |   31 | F      |      1 |
`| 17 | NULL     |   21 | M      |      0 |`
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

#多个条件满足，AND 可以写成 &&
mysql> update stu set age=22,gender='M' where (id=17 and name is null);
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
`| 17 | NULL     |   22 | M      |      0 |`
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

#NULL要写 IS NULL
mysql> update stu set gender='F' where name=null;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 0  Changed: 0  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   22 | `M `     |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

mysql> update stu set gender='F' where name is null;
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   22 | `F `     |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

保证无法在没有条件的情况下更新所有

-U, --i-am-a-dummy Synonym for option --safe-updates, -U.

#该配置还可以写到配置文件中
[root@localhost ~ 14:01:01]# vim /etc/my.cnf.d/client.cnf
[root@localhost ~ 14:07:35]# cat /etc/my.cnf.d/client.cnf
#
# These two groups are read by the client library
# Use it for options that affect all clients, but not the server
#


[client]
`safe-updates`

# This group is not read by mysql client library,
# If you use the same .cnf file for MySQL and MariaDB,
# use it for MariaDB-only client options
[client-mariadb]


[root@localhost ~ 14:07:39]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use db1;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   22 | F      |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

#无法完全更新
mysql> update stu set age=22;
ERROR 1175 (HY000): You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column.

mysql> update stu set age=22 where name='test3';
ERROR 1175 (HY000): You are using safe update mode and you tried to update a table without a WHERE that uses a KEY column.

#必须要指定主键
mysql> update stu set age=22 where id=17;
Query OK, 0 rows affected (0.00 sec)
Rows matched: 1  Changed: 0  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |  ` 22 `| F      |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

3.6.3 删除数据

格式

DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
tbl_name[.*] [, tbl_name[.*]] ...
FROM table_references
[WHERE where_condition]
DELETE [LOW_PRIORITY] [QUICK] [IGNORE]
FROM tbl_name[.*] [, tbl_name[.*]] ...
USING table_references
[WHERE where_condition]

范例

#查看全部数据
mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 10 | xiaoming |   30 | F      |      0 |
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   22 | F      |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
11 rows in set (0.00 sec)

#根据条件删除
mysql> delete from stu where id=10;
Query OK, 1 row affected (0.00 sec)

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 11 | xiaohong |   30 | F      |      0 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   22 | F      |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
10 rows in set (0.00 sec)

在直实生产环境中，一般不会对数据做物理删除，而是用字段来标记为逻辑删除，将对应字段值设为某个特定项(is_del )，(is_del=1)认为是己删除

mysql> update stu set is_del=1 where id=11;
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0

mysql> select * from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 11 | xiaohong |   30 | F      |      1 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   22 | F      |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
10 rows in set (0.00 sec)

3.7 DQL 语句

格式

mysql> help select;
Name: 'SELECT'
Description:
Syntax:
SELECT
    [ALL | DISTINCT | DISTINCTROW ]
    [HIGH_PRIORITY]
    [STRAIGHT_JOIN]
    [SQL_SMALL_RESULT] [SQL_BIG_RESULT] [SQL_BUFFER_RESULT]
    [SQL_NO_CACHE] [SQL_CALC_FOUND_ROWS]
    select_expr [, select_expr] ...
    [into_option]
    [FROM table_references
      [PARTITION partition_list]]
    [WHERE where_condition]
    [GROUP BY {col_name | expr | position}, ... [WITH ROLLUP]]
    [HAVING where_condition]
    [WINDOW window_name AS (window_spec)
        [, window_name AS (window_spec)] ...]
    [ORDER BY {col_name | expr | position}
      [ASC | DESC], ... [WITH ROLLUP]]
    [LIMIT {[offset,] row_count | row_count OFFSET offset}]
    [into_option]
    [FOR {UPDATE | SHARE}
        [OF tbl_name [, tbl_name] ...]
        [NOWAIT | SKIP LOCKED]
      | LOCK IN SHARE MODE]
    [into_option]

into_option: {
    INTO OUTFILE 'file_name'
        [CHARACTER SET charset_name]
        export_options
  | INTO DUMPFILE 'file_name'
  | INTO var_name [, var_name] ...
}

SELECT is used to retrieve rows selected from one or more tables, and
can include UNION statements and subqueries. See [HELP UNION], and
https://dev.mysql.com/doc/refman/8.0/en/subqueries.html. A SELECT
statement can start with a WITH clause to define common table
expressions accessible within the SELECT. See
https://dev.mysql.com/doc/refman/8.0/en/with.html.

The most commonly used clauses of SELECT statements are these:

o Each select_expr indicates a column that you want to retrieve. There
  must be at least one select_expr.

o table_references indicates the table or tables from which to retrieve
  rows. Its syntax is described in [HELP JOIN].

o SELECT supports explicit partition selection using the PARTITION
  clause with a list of partitions or subpartitions (or both) following
  the name of the table in a table_reference (see [HELP JOIN]). In this
  case, rows are selected only from the partitions listed, and any
  other partitions of the table are ignored. For more information and
  examples, see
  https://dev.mysql.com/doc/refman/8.0/en/partitioning-selection.html.

o The WHERE clause, if given, indicates the condition or conditions
  that rows must satisfy to be selected. where_condition is an
  expression that evaluates to true for each row to be selected. The
  statement selects all rows if there is no WHERE clause.

  In the WHERE expression, you can use any of the functions and
  operators that MySQL supports, except for aggregate (group)
  functions. See
  https://dev.mysql.com/doc/refman/8.0/en/expressions.html, and
  https://dev.mysql.com/doc/refman/8.0/en/functions.html.

SELECT can also be used to retrieve rows computed without reference to
any table.

URL: https://dev.mysql.com/doc/refman/8.0/en/select.html

说明

字段显示可以使用别名：col1 AS alias1,col2 AS alias2，...

WHERE子句：指明过滤条件以实现"选择"的功能

过滤条件：布尔型表达式

算术操作符：+,-,*,/，%

比较操作符：=，<=>(相等或都为空）,<>，!=(非标准SQL，>，>=，<，<=

范围查询：BETWEEN min_num AND max_num

不连续的查询：IN(element1，element2，...)

空查询：IS NULL,，IS NOT NULL

DISTINCT去除重复行，范例：SELECT DISTINCT gender FROM students;

模糊查询：LIKE使用%表示任意长度的任意字符_表示任意单个字符

RLIKE：正则表达式，索引失效，不建议使用

REGEXP：匹配字符串可用正则表达式书写模式，同上

逻辑操作符：NOT，AND，OR，XOR

GROUPBY：根据指定的条件把查询结果进行"分组"以用于做"聚合"运算

常见聚合函数：count)，sum()，max(),min()，avg()，注意：聚合函数不对null统计

HAVING：对分组聚合运算后的结果指定过滤条件

一旦分组group by，select语句后只跟分组的字段，聚合函数

ORDERBY：根据指定的字段对查询结果进行排序

升序：ASC

降序：DESC

LIMIT[offset,]row_count]：对查询的结果进行输出行数数量限制，跳过offset，显示row_count 行，offset默为值为0。

对查询结果中的数据请求施加"锁"

FOR UPDATE：写锁，独占或排它锁，只有一个读和写操作

LOCK IN SHARE MODE：读锁，共享锁，同时多个读操作

3.7.1 单表操作

范例：查字符串和变量

#直接查字符串
mysql> select 123;
+-----+
| 123 |
+-----+
| 123 |
+-----+
1 row in set (0.00 sec)

#指定别名
mysql> select 'dyx' as 'dengyunxin';
+------------+
| dengyunxin |
+------------+
| dyx        |
+------------+
1 row in set (0.00 sec)

#数学计算
mysql> select 1+2*3;
+-------+
| 1+2*3 |
+-------+
|     7 |
+-------+
1 row in set (0.00 sec)

#查询变量
mysql> select @@port;
+--------+
| @@port |
+--------+
|   3306 |
+--------+
1 row in set (0.00 sec)

#查询函数
mysql> select now();
+---------------------+
| now()               |
+---------------------+
| 2025-12-05 14:25:45 |
+---------------------+
1 row in set (0.00 sec)

范例：指定字段和查询条件

#全表扫描
mysql> select *  from stu;
+----+----------+------+--------+--------+
| id | name     | age  | gender | is_del |
+----+----------+------+--------+--------+
| 11 | xiaohong |   30 | F      |      1 |
| 12 | zhangsan |   30 | F      |      0 |
| 13 | xiaozhou |   30 | F      |      1 |
| 14 | test1    |   30 | F      |      1 |
| 15 | test2    |   21 | M      |      1 |
| 16 | test3    |   31 | F      |      1 |
| 17 | NULL     |   22 | F      |      0 |
| 18 | xiaohong |   31 | F      |      1 |
| 19 | xiaohong |   31 | F      |      1 |
| 20 | zhangsan |   31 | F      |      1 |
+----+----------+------+--------+--------+
10 rows in set (0.00 sec)

#查询指定字段
mysql> select id as 学号 , name as 姓名 , age as 年龄  from stu;
+--------+----------+--------+
| 学号   | 姓名     | 年龄   |
+--------+----------+--------+
|     11 | xiaohong |     30 |
|     12 | zhangsan |     30 |
|     13 | xiaozhou |     30 |
|     14 | test1    |     30 |
|     15 | test2    |     21 |
|     16 | test3    |     31 |
|     17 | NULL     |     22 |
|     18 | xiaohong |     31 |
|     19 | xiaohong |     31 |
|     20 | zhangsan |     31 |
+--------+----------+--------+
10 rows in set (0.00 sec)

#根据条件查询
mysql> select id,name from stu where id=11;
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
+----+----------+
1 row in set (0.00 sec)


#多条
mysql> select id,name from stu where id in (11,15,19);
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 15 | test2    |
| 19 | xiaohong |
+----+----------+
3 rows in set (0.00 sec)

#and 可以写为 &&
mysql> select id,name from stu where id>=11 and id<14;
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 12 | zhangsan |
| 13 | xiaozhou |
+----+----------+
3 rows in set (0.00 sec)

#or 可以写为 ||
mysql> select id,name from stu where id<=12 or id>19;
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 12 | zhangsan |
| 20 | zhangsan |
+----+----------+
3 rows in set (0.00 sec)

范例：NULL值

#语法错误
mysql> select id,name,age from stu where name=null;
Empty set (0.00 sec)

#null值
mysql> select id,name,age from stu where name is null;
+----+------+------+
| id | name | age  |
+----+------+------+
| 17 | NULL |   22 |
+----+------+------+
1 row in set (0.00 sec)

#非null值
mysql> select id,name,age from stu where name is not null;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
| 11 | xiaohong |   30 |
| 12 | zhangsan |   30 |
| 13 | xiaozhou |   30 |
| 14 | test1    |   30 |
| 15 | test2    |   21 |
| 16 | test3    |   31 |
| 18 | xiaohong |   31 |
| 19 | xiaohong |   31 |
| 20 | zhangsan |   31 |
+----+----------+------+
9 rows in set (0.00 sec)

范例：模糊匹配

#以指定字符开头
mysql> select id,name from stu where name like 'x%';
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 13 | xiaozhou |
| 18 | xiaohong |
| 19 | xiaohong |
+----+----------+
4 rows in set (0.00 sec)

#以指定字符开头
mysql> select id,name from stu where name like 'xiao%';
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 13 | xiaozhou |
| 18 | xiaohong |
| 19 | xiaohong |
+----+----------+
4 rows in set (0.00 sec)

#以指定字符结尾
mysql> select id,name from stu where name like '%ng';
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 18 | xiaohong |
| 19 | xiaohong |
+----+----------+
3 rows in set (0.00 sec)

#包含指定字符串
mysql> select id,name from stu where name like '%ou%';
+----+----------+
| id | name     |
+----+----------+
| 13 | xiaozhou |
+----+----------+
1 row in set (0.00 sec)

#多个LIKE
mysql> select id,name from stu where name like '%n%' or name like '%i%';
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 12 | zhangsan |
| 13 | xiaozhou |
| 18 | xiaohong |
| 19 | xiaohong |
| 20 | zhangsan |
+----+----------+
6 rows in set (0.00 sec)

范例：区域间过滤

#连续
mysql> select id,name from stu where id between 12 and 15;
+----+----------+
| id | name     |
+----+----------+
| 12 | zhangsan |
| 13 | xiaozhou |
| 14 | test1    |
| 15 | test2    |
+----+----------+
4 rows in set (0.00 sec)

#取反
mysql> select id,name from stu where id not between 12 and 15;
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 16 | test3    |
| 17 | NULL     |
| 18 | xiaohong |
| 19 | xiaohong |
| 20 | zhangsan |
+----+----------+
6 rows in set (0.00 sec)

#不连续
mysql> select id,name from stu where id in (12,15,19);
+----+----------+
| id | name     |
+----+----------+
| 12 | zhangsan |
| 15 | test2    |
| 19 | xiaohong |
+----+----------+
3 rows in set (0.00 sec)

#不连续取反
mysql> select id,name from stu where id not in (12,15,19);
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 13 | xiaozhou |
| 14 | test1    |
| 16 | test3    |
| 17 | NULL     |
| 18 | xiaohong |
| 20 | zhangsan |
+----+----------+
7 rows in set (0.00 sec)

范例：统计和分组

#统计表中的记录条数
mysql> select count(*) as total from stu;
+-------+
| total |
+-------+
|    10 |
+-------+
1 row in set (0.00 sec)

#age字段中有null，不统计
mysql> select count(age)  from stu;
+------------+
| count(age) |
+------------+
|         10 |
+------------+
1 row in set (0.00 sec)

mysql> select count(id)  from stu;
+-----------+
| count(id) |
+-----------+
|        10 |
+-----------+
1 row in set (0.00 sec)

#最大值，最小值，平均值
mysql> select max(id),min(id),avg(age) from stu;
+---------+---------+----------+
| max(id) | min(id) | avg(age) |
+---------+---------+----------+
|      20 |      11 |  28.7000 |
+---------+---------+----------+
1 row in set (0.00 sec)

#求和
mysql> select sum(age) from stu;
+----------+
| sum(age) |
+----------+
|      287 |
+----------+
1 row in set (0.00 sec)

#分组统计
mysql> select sum(age),gender from stu group by gender;
+----------+--------+
| sum(age) | gender |
+----------+--------+
|      266 | F      |
|       21 | M      |
+----------+--------+
2 rows in set (0.00 sec)

#分组统计
mysql> select count(*),gender from stu group by gender;
+----------+--------+
| count(*) | gender |
+----------+--------+
|        9 | F      |
|        1 | M      |
+----------+--------+
2 rows in set (0.00 sec)

#分组带where条件
mysql> select count(*),max(id),avg(age),gender from stu where age is not null group by gender;
+----------+---------+----------+--------+
| count(*) | max(id) | avg(age) | gender |
+----------+---------+----------+--------+
|        9 |      20 |  29.5556 | F      |
|        1 |      15 |  21.0000 | M      |
+----------+---------+----------+--------+
2 rows in set (0.00 sec)

mysql> select count(*) as total,max(id),avg(age),gender from stu where age is not null group by gender;
+-------+---------+----------+--------+
| total | max(id) | avg(age) | gender |
+-------+---------+----------+--------+
|     9 |      20 |  29.5556 | F      |
|     1 |      15 |  21.0000 | M      |
+-------+---------+----------+--------+
2 rows in set (0.00 sec)


#分组后过滤
mysql> select count(*) as total,max(id),avg(age),gender from stu where age is not null group by gender having total=3;
Empty set (0.00 sec)

#分组统计
mysql> select count(*),max(id),avg(age),gender from stu group by gender;
+----------+---------+----------+--------+
| count(*) | max(id) | avg(age) | gender |
+----------+---------+----------+--------+
|        9 |      20 |  29.5556 | F      |
|        1 |      15 |  21.0000 | M      |
+----------+---------+----------+--------+
2 rows in set (0.00 sec)

范例：排序

#默认按ID升序排列
mysql> select  id,name,age from stu;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
| 11 | xiaohong |   30 |
| 12 | zhangsan |   30 |
| 13 | xiaozhou |   30 |
| 14 | test1    |   30 |
| 15 | test2    |   21 |
| 16 | test3    |   31 |
| 17 | NULL     |   22 |
| 18 | xiaohong |   31 |
| 19 | xiaohong |   31 |
| 20 | zhangsan |   31 |
+----+----------+------+
10 rows in set (0.00 sec)

mysql> select  id,name,age from stu order by id;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
| 11 | xiaohong |   30 |
| 12 | zhangsan |   30 |
| 13 | xiaozhou |   30 |
| 14 | test1    |   30 |
| 15 | test2    |   21 |
| 16 | test3    |   31 |
| 17 | NULL     |   22 |
| 18 | xiaohong |   31 |
| 19 | xiaohong |   31 |
| 20 | zhangsan |   31 |
+----+----------+------+
10 rows in set (0.00 sec)

mysql> select  id,name,age from stu order by id asc;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
| 11 | xiaohong |   30 |
| 12 | zhangsan |   30 |
| 13 | xiaozhou |   30 |
| 14 | test1    |   30 |
| 15 | test2    |   21 |
| 16 | test3    |   31 |
| 17 | NULL     |   22 |
| 18 | xiaohong |   31 |
| 19 | xiaohong |   31 |
| 20 | zhangsan |   31 |
+----+----------+------+
10 rows in set (0.00 sec)

#降序
mysql> select  id,name,age from stu order by id desc;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
| 20 | zhangsan |   31 |
| 19 | xiaohong |   31 |
| 18 | xiaohong |   31 |
| 17 | NULL     |   22 |
| 16 | test3    |   31 |
| 15 | test2    |   21 |
| 14 | test1    |   30 |
| 13 | xiaozhou |   30 |
| 12 | zhangsan |   30 |
| 11 | xiaohong |   30 |
+----+----------+------+
10 rows in set (0.00 sec)

#降序变升序
mysql> select  id,name,age from stu order by -id desc;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
| 11 | xiaohong |   30 |
| 12 | zhangsan |   30 |
| 13 | xiaozhou |   30 |
| 14 | test1    |   30 |
| 15 | test2    |   21 |
| 16 | test3    |   31 |
| 17 | NULL     |   22 |
| 18 | xiaohong |   31 |
| 19 | xiaohong |   31 |
| 20 | zhangsan |   31 |
+----+----------+------+
10 rows in set (0.00 sec)

#用分组结果排序
mysql> select sum(age) sum_age,avg(age) avg_age,gender from stu where name is not null group by gender order by sum_age asc;
+---------+---------+--------+
| sum_age | avg_age | gender |
+---------+---------+--------+
|      21 | 21.0000 | M      |
|     244 | 30.5000 | F      |
+---------+---------+--------+
2 rows in set (0.00 sec)

范例：去重

mysql> select id ,name,age from stu order by age desc;
+----+----------+------+
| id | name     | age  |
+----+----------+------+
| 16 | test3    |   31 |
| 18 | xiaohong |   31 |
| 19 | xiaohong |   31 |
| 20 | zhangsan |   31 |
| 11 | xiaohong |   30 |
| 12 | zhangsan |   30 |
| 13 | xiaozhou |   30 |
| 14 | test1    |   30 |
| 17 | NULL     |   22 |
| 15 | test2    |   21 |
+----+----------+------+
10 rows in set (0.00 sec)

mysql> select distinct age from stu order by age desc;
+------+
| age  |
+------+
|   31 |
|   30 |
|   22 |
|   21 |
+------+
4 rows in set (0.00 sec)

mysql> select distinct(age) from stu order by age desc;
+------+
| age  |
+------+
|   31 |
|   30 |
|   22 |
|   21 |
+------+
4 rows in set (0.00 sec)

范例：分页

mysql> select id,name from stu;
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 12 | zhangsan |
| 13 | xiaozhou |
| 14 | test1    |
| 15 | test2    |
| 16 | test3    |
| 17 | NULL     |
| 18 | xiaohong |
| 19 | xiaohong |
| 20 | zhangsan |
+----+----------+
10 rows in set (0.00 sec)

#第一页，每页3条记录
mysql> select id,name from stu limit 0,3;
+----+----------+
| id | name     |
+----+----------+
| 11 | xiaohong |
| 12 | zhangsan |
| 13 | xiaozhou |
+----+----------+
3 rows in set (0.01 sec)

#第二页，每页3条记录
mysql> select id,name from stu limit 3,3;
+----+-------+
| id | name  |
+----+-------+
| 14 | test1 |
| 15 | test2 |
| 16 | test3 |
+----+-------+
3 rows in set (0.00 sec)


mysql> select id,name from stu limit 5,4;
+----+----------+
| id | name     |
+----+----------+
| 16 | test3    |
| 17 | NULL     |
| 18 | xiaohong |
| 19 | xiaohong |
+----+----------+
4 rows in set (0.00 sec)

3.8 MySQL 用户管理

MySQL服务的账户是独立存在的，只用于MySQL服务的登录验证。

虚拟用户：给服务和应用使用的用户账号。

系统用户：Linux系统使用的用户账号

在MySQL服务中，用户组成包括用户名，主机，密码等。

Host指主机，表示只有在该主机上，才能使用对应的账号连接MySQL服务器，主机限制了账号可以登录的位置。用户名可以相同，主机也可以相同，用户名和主机组合起来才能标识一个唯一用户。

其它数据库系统，例如SQLServer，Oracle等都没有此限制，只要账号和密码能校验通过即可登录。这也是MySQL与其它数据库系统的一个不同之处。

Host可以写成主机名，IP地址，网段。可以用%，*来表示通配符，**%**表示任意长度的任意字符，*表示一个字符。

范例：

#主机名
dyx@'mysql.dyx.cloud'
dyx'localhost'
#IP地址
dyx@'10.0.0.110'
dyx@'172.16.10.110'
#网段
dyx@′10.0.0.0/255.255.0.0'
dyx@′172.16.10.0/255.255.255.0'
#通配符
dyx@′10.0.%.%
dyx@'172.16._.%'

MySQL8.0中默认没有可以远程登陆的用户

#前三个是MySQL服务自身使用
mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed

mysql> select host,user from user;
+-----------+------------------+
| host      | user             |
+-----------+------------------+
| localhost | mysql.infoschema |
| localhost | mysql.session    |
| localhost | mysql.sys        |
| localhost | root             |
+-----------+------------------+
4 rows in set (0.00 sec)

#现在使用的是第四个
mysql> select user();
+----------------+
| user()         |
+----------------+
| root@localhost |
+----------------+
1 row in set (0.00 sec)

#也可以用status命令来查看
mysql> status
--------------
mysql  Ver 8.0.26 for Linux on x86_64 (Source distribution)

Connection id:          9
Current database:       mysql
Current user:           root@localhost
SSL:                    Not in use
Current pager:          stdout
Using outfile:          ''
Using delimiter:        ;
Server version:         8.0.26 Source distribution
Protocol version:       10
Connection:             Localhost via UNIX socket
Server characterset:    utf8mb4
Db     characterset:    utf8mb4
Client characterset:    utf8mb4
Conn.  characterset:    utf8mb4
UNIX socket:            /var/lib/mysql/mysql.sock
Binary data as:         Hexadecimal
Uptime:                 2 hours 45 min 50 sec

Threads: 2  Questions: 140  Slow queries: 0  Opens: 202  Flush tables: 3  Open tables: 121  Queries per second avg: 0.014

Note that you are running in safe_update_mode:
UPDATEs and DELETEs that don't use a key in the WHERE clause are not allowed.
(One can force an UPDATE/DELETE by adding LIMIT # at the end of the command.)
SELECT has an automatic 'LIMIT 1000' if LIMIT is not used.
Max number of examined row combination in a join is set to: 1000000

1,线mysql server关机克隆产生mysql_client

2.记录2台机器地址

192.168.108.128
192.168.108.139

3.mysql_server创建远程连接账号

mysql> create user test@'192.168.108.%' identified by '123';
Query OK, 0 rows affected (0.01 sec)

4.mysql_server关闭防火墙，

[root@localhost ~ 16:28:48]# systemctl stop firewalld

5.mysql_client连接mysql_server

[root@localhost ~ 16:28:30]# mysql -utest -p123 -h192.168.108.128

创建用户：CREATE USER

[root@localhost my.cnf.d 09:32:26]# ls
client.cnf  mysql-default-authentication-plugin.cnf  mysql-server.cnf

[root@localhost my.cnf.d 09:32:35]# vim client.cnf
[root@localhost my.cnf.d 09:32:44]# cat client.cnf
#
# These two groups are read by the client library
# Use it for options that affect all clients, but not the server
#


[client]

# This group is not read by mysql client library,
# If you use the same .cnf file for MySQL and MariaDB,
# use it for MariaDB-only client options
[client-mariadb]

mysql> create user test2@'192.168.108.%' identified by '123456';
Query OK, 0 rows affected (0.02 sec)#格式
CREATE USER 'USERNAME'@'HOST' [IDENTIFIED BY 'password'];

#范例
mysql> create user test2@'192.168.108.%' identified by '123456';
Query OK, 0 rows affected (0.02 sec)

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select host,user from user;
+---------------+------------------+
| host          | user             |
+---------------+------------------+
| 192.168.108.% | test             |
`| 192.168.108.% | test2            |`
| localhost     | mysql.infoschema |
| localhost     | mysql.session    |
| localhost     | mysql.sys        |
| localhost     | root             |
+---------------+------------------+
6 rows in set (0.00 sec)

重命名用户：RENAME USER

RENAME USER 'USERNAME'@'HOST' TO 'USERNAME'@'HOST';

删除用户：DROP USER

DROP USER 'USERNAME'@'HOST'

mysql> drop user test2@'192.168.108.%';
Query OK, 0 rows affected (0.01 sec)

mysql> select host,user from user;
+---------------+------------------+
| host          | user             |
+---------------+------------------+
| 192.168.108.% | test             |
| localhost     | mysql.infoschema |
| localhost     | mysql.session    |
| localhost     | mysql.sys        |
| localhost     | root             |
+---------------+------------------+
5 rows in set (0.00 sec)

修改密码

新版mysql中用户密码可以保存在mysql.user表的 authentication_string字段中，己经取消了password字段。

mariadb中某些版本 authentication_string，password字段共存，I日版以password字段为准，新版以authentication_string为准。

#方式一
SET PASSWORD FOR 'user'@'host' = PASSWORD('password');

#mysql8.0中取消了PASSWORD方法
mysql> set password for root@'localhost'='123456';
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '('123456')' at line 1
#MariaDB中还有


#在MYSQL8.0中可以使用此写法
#MYSQL8.0中的密码是放在 mysql.user 表中 authentication_string 字段中，但MariaDB中还保留了PASSWORD字段
mysql> select host,user,authentication_string from mysql.user;
+---------------+------------------+------------------------------------------------------------------------+
| host          | user             | authentication_string                                                  |
+---------------+------------------+------------------------------------------------------------------------+
| 192.168.108.% | test             | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257                              |
| localhost     | mysql.infoschema | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| localhost     | mysql.session    | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| localhost     | mysql.sys        | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| localhost     | root             |                                                                        |
+---------------+------------------+------------------------------------------------------------------------+
5 rows in set (0.00 sec)

#更新密码
mysql> set password for  root@'localhost'='123456';
Query OK, 0 rows affected (0.00 sec)

#方式二
语法：ALTER USER test@'%' IDENTIFIED BY '123456';
#此方法通用
mysql> alter user root@'localhost' identified by '123456';
Query OK, 0 rows affected (0.00 sec)

mysql> select host,user,authentication_string from mysql.user;
+---------------+------------------+------------------------------------------------------------------------+
| host          | user             | authentication_string                                                  |
+---------------+------------------+------------------------------------------------------------------------+
| 192.168.108.% | test             | *23AE809DDACAF96AF0FD78ED04B6A265E05AA257                              |
| localhost     | mysql.infoschema | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| localhost     | mysql.session    | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| localhost     | mysql.sys        | $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED |
| localhost     | root             | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9                              |
+---------------+------------------+------------------------------------------------------------------------+
5 rows in set (0.00 sec)
[root@localhost my.cnf.d 09:37:18]# mysql -uroot -p123456
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 12
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> quit
Bye

#方法三
[root@localhost my.cnf.d 09:37:34]# mysqladmin -uroot -p123456 password abcde
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.
[root@localhost my.cnf.d 09:37:59]# cd
[root@localhost ~ 09:38:04]# mysql -uroot -pabcde
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 14
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql>

忘记密码

#方式一，保留原有数据

#1 启动时添加指定项
--skip-grant-tables
--skip-networking

#2 使用UPDATE命令修改管理员密码
#3 移除配置项重启

#方式一范例
[root@localhost ~ 09:44:20]# vim /etc/my.cnf.d/mysql-server.cnf
[root@localhost ~ 09:45:04]# tail -2 /etc/my.cnf.d/mysql-server.cnf
skip-grant-tables
skip-networking
[root@localhost ~ 09:45:11]# systemctl restart mysqld.service

[root@localhost ~ 09:45:25]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

#步骤1
mysql> update mysql.user set authentication_string='' where user='root' and host='localhost';
Query OK, 1 row affected (0.01 sec)
Rows matched: 1  Changed: 1  Warnings: 0

#步骤2
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

#再执行下面命令
mysql> alter user root@'localhost' identified by '123';
Query OK, 0 rows affected (0.00 sec)

mysql> quit
Bye

[root@localhost ~ 09:47:18]# mysql -uroot -p123
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 9
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> quit
Bye

范例：删库跑路之清空root密码方法

！！！学完就忘

#方式二，会清除所有数据
#停止服务[root@localhost ~ 09:47:49]# systemctl stop mysqld.service
rm [root@localhost ~ 09:48:01]# rm -rf /var/lib/mysql/*
[root@localhost ~ 09:48:13]# systemctl start mysqld.service
[root@localhost ~ 09:48:25]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 7
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| mysql              |
| performance_schema |
| sys                |
+--------------------+
4 rows in set (0.01 sec)

[root@localhost ~ 09:57:09]# vim /etc/my.cnf.d/mysql-server.cnf
[root@localhost ~ 09:57:25]# cat /etc/my.cnf.d/mysql-server.cnf
#
# This group are read by MySQL server.
# Use it for options that only the server (but not clients) should see
#
# For advice on how to change settings please see
# http://dev.mysql.com/doc/refman/en/server-configuration-defaults.html

# Settings user and group are ignored when systemd is used.
# If you need to run mysqld under a different user or group,
# customize your systemd unit file for mysqld according to the
# instructions in http://fedoraproject.org/wiki/Systemd

[mysqld]
datadir=/var/lib/mysql
socket=/var/lib/mysql/mysql.sock
log-error=/var/log/mysql/mysqld.log
pid-file=/run/mysqld/mysqld.pid


[root@localhost ~ 09:58:17]# systemctl restart mysqld.service

在当前MYSQL服务中添加用户

[root@localhost ~ 09:58:31]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed


#需要远程连接本mysql的客户端地址
mysql>  create user root@'192.168.108.1' identified by '123456';
Query OK, 0 rows affected (0.01 sec)

mysql> select host,user from user;
+---------------+------------------+
| host          | user             |
+---------------+------------------+
| 192.168.108.1 | root             |
| localhost     | mysql.infoschema |
| localhost     | mysql.session    |
| localhost     | mysql.sys        |
| localhost     | root             |
+---------------+------------------+
5 rows in set (0.00 sec)

[root@localhost ~ 09:59:18]# firewall-cmd --add-service=mysql
success
[root@localhost ~ 09:59:35]# firewall-cmd --add-service=mysql --permanent
success

C:\Users\86189>mysql -uroot -h192.168.108.128 -p123456
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 10
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2025, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

#查看数据库
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)

#查看当前客户端连接时适用的用户名和主机
mysql> select user();
+--------------------+
| user()             |
+--------------------+
| root@192.168.108.1 |
+--------------------+
1 row in set (0.00 sec)

#查看线程
mysql> show processlist;
+----+------+---------------------+------+---------+------+-------+------------------+
| Id | User | Host                | db   | Command | Time | State | Info             |
+----+------+---------------------+------+---------+------+-------+------------------+
| 10 | root | 192.168.108.1:49751 | NULL | Query   |    0 | init  | show processlist |
+----+------+---------------------+------+---------+------+-------+------------------+
1 row in set (0.00 sec)

#没有权限
mysql> use mysql;
ERROR 1044 (42000): Access denied for user 'root'@'192.168.108.1' to database 'mysql'

mysql> create database db1;
ERROR 1044 (42000): Access denied for user 'root'@'192.168.108.1' to database 'db1'
mysql>

3.9 权限管理和DCL语句

在MySQL服务中，新创建的用户仅仅只能连接，没有操作权限，需要配置相应的权限后才能使用。

3.9.1 权限类别

管理类

CREATE USER，FILE，SUPER，SHOW DATABASES，RELOAD，SHUTDOWN，REPLICATION SLAVE，REPLICATION CLIENT，LOCK TABLES，PROCESS，CREATE TEMPORARY TABLES

程序类针对FUNCTION **、PROCEDURE 、TRIGGER

CREATE，ALTER，DROP，EXCUTE

库和表级别针对DATABASE 、TABLE

ALTER，CREATE，CREATE VIEW，DROP INDEX，SHOW VIEW，WITH GRANT OPTION(将自己获得的权限转赠给其他用户）

数据操作

SELECT，INSERT，DELETE，UPDATE

字段级别

SELECT(col1,coI2.,...)，UPDATE(col1,col2,...)，INSERT(col1,col2,...)

所有权限

ALL PRIVILEGES或ALL

3.9.2 授权

格式

[root@localhost ~ 09:59:40]# mysql
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 11
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> help grant;
Name: 'GRANT'
Description:
Syntax:
GRANT
    priv_type [(column_list)]
      [, priv_type [(column_list)]] ...
    ON [object_type] priv_level
    TO user_or_role [, user_or_role] ...
    [WITH GRANT OPTION]
    [AS user
        [WITH ROLE
            DEFAULT
          | NONE
          | ALL
          | ALL EXCEPT role [, role ] ...
          | role [, role ] ...
        ]
    ]
}

GRANT PROXY ON user_or_role
    TO user_or_role [, user_or_role] ...
    [WITH GRANT OPTION]

GRANT role [, role] ...
    TO user_or_role [, user_or_role] ...
    [WITH ADMIN OPTION]

object_type: {
    TABLE
  | FUNCTION
  | PROCEDURE
}

priv_level: {
    *
  | *.*
  | db_name.*
  | db_name.tbl_name
  | tbl_name
  | db_name.routine_name
}

user_or_role: {
    user (see https://dev.mysql.com/doc/refman/8.0/en/account-names.html)
  | role (see https://dev.mysql.com/doc/refman/8.0/en/role-names.html)
}

The GRANT statement enables system administrators to grant privileges
and roles, which can be granted to user accounts and roles. These
syntax restrictions apply:

o GRANT cannot mix granting both privileges and roles in the same
  statement. A given GRANT statement must grant either privileges or
  roles.

o The ON clause distinguishes whether the statement grants privileges
  or roles:

  o With ON, the statement grants privileges.

  o Without ON, the statement grants roles.

  o It is permitted to assign both privileges and roles to an account,
    but you must use separate GRANT statements, each with syntax
    appropriate to what is to be granted.

For more information about roles, see
https://dev.mysql.com/doc/refman/8.0/en/roles.html.

To grant a privilege with GRANT, you must have the GRANT OPTION
privilege, and you must have the privileges that you are granting.
(Alternatively, if you have the UPDATE privilege for the grant tables
in the mysql system schema, you can grant any account any privilege.)
When the read_only system variable is enabled, GRANT additionally
requires the CONNECTION_ADMIN privilege (or the deprecated SUPER
privilege).

GRANT either succeeds for all named users and roles or rolls back and
has no effect if any error occurs. The statement is written to the
binary log only if it succeeds for all named users and roles.

The REVOKE statement is related to GRANT and enables administrators to
remove account privileges. See [HELP REVOKE].

Each account name uses the format described in
https://dev.mysql.com/doc/refman/8.0/en/account-names.html. Each role
name uses the format described in
https://dev.mysql.com/doc/refman/8.0/en/role-names.html. For example:

GRANT ALL ON db1.* TO 'jeffrey'@'localhost';
GRANT 'role1', 'role2' TO 'user1'@'localhost', 'user2'@'localhost';
GRANT SELECT ON world.* TO 'role3';

The host name part of the account or role name, if omitted, defaults to
'%'.

Normally, a database administrator first uses CREATE USER to create an
account and define its nonprivilege characteristics such as its
password, whether it uses secure connections, and limits on access to
server resources, then uses GRANT to define its privileges. ALTER USER
may be used to change the nonprivilege characteristics of existing
accounts. For example:

CREATE USER 'jeffrey'@'localhost' IDENTIFIED BY 'password';
GRANT ALL ON db1.* TO 'jeffrey'@'localhost';
GRANT SELECT ON db2.invoice TO 'jeffrey'@'localhost';
ALTER USER 'jeffrey'@'localhost' WITH MAX_QUERIES_PER_HOUR 90;

From the mysql program, GRANT responds with Query OK, 0 rows affected
when executed successfully. To determine what privileges result from
the operation, use SHOW GRANTS. See [HELP SHOW GRANTS].

URL: https://dev.mysql.com/doc/refman/8.0/en/grant.html

#priv_type 要授予的权限ALL [PRIVILEGES]
#object_type 对象的类型TABLE|FUNCTION|PROCEDURE
#priv_level 范围*|*.*|db_name.*|db_name.tbl_name|tbl_name|db_name.routine_name(指定库的函数，存储过程，触发器)
#with_option 选项
#GRANT OPTION 可以将自己的权限授权给其它账号
#MAX_QUERIES_PER_HOUR N 每小时最大查询次数
#MAX_UPDATES_PER_HOUR N 每小时最大更新次数
#MAX_CONNECTIONS_PER_HOUR N 每小时最大连接次数
#MAX_USER_CONNECTIONS N 最大用户连接数
#MAX_USER_CONNECTIONS 指的是瞬间的并发连接数，而MAX_CONNECTIONS_PER_HOUR指的是每小时累计的最大连接次数
#资源限制是对某一账号进行累计的，而不是对账号的一次连接进行累计的，当资源限制到达后，账号的任何一次相关操作都会被拒

范例：

#只能查询，插入指定字段
GRANT SELECT(col1),INSERT(col1,col2) ON mydb.mytbl TO 'someuser'@'somehost';

#有指定库的所有权限
GRANT ALL ON wordpress.* TO wordpress@'10.0.0.%';

#授予所有权限
GRANT ALL PRIVILEGES ON *.* TO 'root'@'10.0.0.%' WITH GRANT OPTION;

#创建用户和授权同时执行的方式在MySQL8.0取消了
GRANT ALL ON wordpress.* TO wordpress@'192.168.108.%' IDENTIFIED BY 'huawei';
GRANT ALL PRIVILEGES ON *.* TO 'root'@'192.168.108.%' IDENTIFIED BY 'huawei' WITH
GRANT OPTION;

3.9.3 取消权限

格式

REVOKE
priv_type [(column_list)]
[, priv_type [(column_list)]] ...
ON [object_type] priv_level
FROM user_or_role [, user_or_role] ...

范例

REVOKE DELETE ON *.* FROM 'testuser'@'172.16.0.%';
REVOKE ALL ON *.* FROM'testuser'@'172.16.0.%';

REVOKE ALL ON *.* FROM'testuser'@'172.16.0.%';

3.9.4 查看用户权限

格式

#查看指定用户权限
SHOW GRANTS FOR 'user'@'host';
#查看当前使用中的用户的权限
SHOW GRANTS FOR CURRENT_USER[()];

注意

• MariaDB服务进程启动时会读取mysql库中所有授权表至内存。

• GRANT或REVOKE等执行权限操作会保存于系统表中，MariaDB的服务进程通常会自动重读授权表，使之生效。

• 对于不能够或不能及时重读授权表的命令，可手动让MariaDB的服务进程重读授权表：mysql>FLUSH PRIVILEGES。

范例

#本地操作
#创建用户
mysql> create user 'root'@'192.168.108.%' identified by '123456';
Query OK, 0 rows affected (0.00 sec)

mysql> select host,user from mysql.user;
+---------------+------------------+
| host          | user             |
+---------------+------------------+
| `192.168.108.% | root`             |
| 192.168.108.1 | root             |
| localhost     | mysql.infoschema |
| localhost     | mysql.session    |
| localhost     | mysql.sys        |
| localhost     | root             |
+---------------+------------------+
6 rows in set (0.00 sec)

#查看新用户的权限，默认只有 USAGE 权限，只能连接
mysql> show grants for 'root'@'192.168.108.%';
+----------------------------------------------+
| Grants for root@192.168.108.%                |
+----------------------------------------------+
| GRANT USAGE ON *.* TO `root`@`192.168.108.%` |
+----------------------------------------------+
1 row in set (0.00 sec)

#远程连接，远程操作
C:\Users\86189>mysql -uroot -p123456 -h192.168.108.128

#查看权限，远程操作
mysql> SHOW GRANTS FOR CURRENT_USER;
+----------------------------------------------+
| Grants for root@192.168.108.% |
+----------------------------------------------+
| GRANT USAGE ON *.* TO `root`@`192.168.108.%` |
+----------------------------------------------+
1 row in set (0.00 sec)

#无权限创建，远程操作
mysql> create database db1;
ERROR 1044 (42000): Access denied for user 'root'@'192.168.108.%' to database 'db1'

#本地操作
mysql> create database db1;
Query OK, 1 row affected (0.01 sec)

mysql> create database db2;
Query OK, 1 row affected (0.00 sec)

mysql> use db1;
Database changed

mysql> CREATE TABLE student (id int UNSIGNED AUTO_INCREMENT PRIMARY KEY,name VARCHAR(20) NOT NULL,age tinyint UNSIGNED,gender ENUM('M','F') default 'M')ENGINE=InnoDB AUTO_INCREMENT=10 DEFAULT CHARSET=utf8mb4;
Query OK, 0 rows affected (0.01 sec)

mysql> insert student (name,age)values('xiaoming',20);
Query OK, 1 row affected (0.00 sec)

#授权能查看 mysql 中的 user 表，本地操作
mysql> grant select on db1.student to root@'192.168.108.1';
Query OK, 0 rows affected (0.00 sec)

#远程用户再次刷新，远程操作
mysql> SHOW GRANTS FOR CURRENT_USER;
+-----------------------------------------------------------+
| Grants for root@192.168.108.% |
+-----------------------------------------------------------+
| GRANT USAGE ON *.* TO `root`@`192.168.108.%` |
| GRANT SELECT ON `db1`.`student` TO `root`@`192.168.108.%` |
+-----------------------------------------------------------+
2 rows in set (0.00 sec)

#能看到数据库，远程操作
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| db1 |
| information_schema |
+--------------------+
2 rows in set (0.00 sec)

#远程操作
mysql> use db1;
Database changed
mysql> show tables;
+---------------+
| Tables_in_db1 |
+---------------+
| student |
+---------------+
1 row in set (0.00 sec)

#远程操作
mysql> select * from student;
+----+----------+------+--------+
| id | name | age | gender |
+----+----------+------+--------+
| 10 | xiaoming | 20 | M |
+----+----------+------+--------+
1 row in set (0.00 sec)

#没有更新权限，远程操作
mysql> update student set age=25 where id=10;
ERROR 1142 (42000): UPDATE command denied to user 'root'@'192.168.108.1' for
table 'student'

#没有删除权限，远程操作
mysql> delete from student where id=10;
ERROR 1142 (42000): DELETE command denied to user 'root'@'192.168.108.1' for table 'student'

#继续授权，本地操作
mysql> grant update,delete on db1.student to root@'192.168.108.1';
Query OK, 0 rows affected (0.00 sec)

#再次查看，远程操作
mysql> SHOW GRANTS FOR CURRENT_USER;
+---------------------------------------------------------------------------+
| Grants for root@192.168.108.% |
+---------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO `root`@`192.168.108.%` |
| GRANT SELECT, UPDATE, DELETE ON `db1`.`student` TO `root`@`192.168.108.%` |
+---------------------------------------------------------------------------+
2 rows in set (0.00 sec)

#测试，远程操作
mysql> update student set age=25 where id=10;
mysql> select * from student;
+----+----------+------+--------+
| id | name | age | gender |
+----+----------+------+--------+
| 10 | xiaoming | 25 | M |
+----+----------+------+--------+
1 row in set (0.00 sec)
mysql> delete from student where id=10;
mysql> select * from student;
Empty set (0.00 sec)

范例

#创建数据库，本地操作
mysql> create database eshop;
Query OK, 1 row affected (0.00 sec)

#创建用户，本地操作
mysql> create user eshoper@'192.168.108.%' identified by '123456';
Query OK, 0 rows affected (0.01 sec)

#授权，本地操作
mysql> grant all on eshop.* to eshoper@'192.168.108.%';
Query OK, 0 rows affected (0.00 sec)

#远程测试
C:\Users\86189>mysql -ueshoper -p123456 -h192.168.108.128
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 17
Server version: 8.0.26 Source distribution
Copyright (c) 2000, 2025, Oracle and/or its affiliates.
Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> show databases;
+--------------------+
| Database |
+--------------------+
| eshop |
| information_schema |
+--------------------+
2 rows in set (0.00 sec)

#创建表
mysql> use eshop;
Database changed

mysql> create table product (id int,name varchar(10));
Query OK, 0 rows affected (0.10 sec)

mysql> show tables;
+-----------------+
| Tables_in_eshop |
+-----------------+
| product |
+-----------------+
1 row in set (0.00 sec)

3.10MySQL 图形化远程管理工具

在MySQL数据库中创建用户并授权后，可以使用相关图形化工具进行远程的管理。

常见的图形化管理工具包括Navicat，SQLyog，DBbear等。

3.10.1 Navicat 工具

3.10.2 SQLyog 工具

3.11 实现基于LAMP架构的开源网站

3.11.1 LAMP 架构说明

LAMP是指一组通常一起使用来运行动态网站的自由软件名称首字母的缩写。

• L是指Linux操作系统。

• A是指Apache，用来提供Web服务。

• M指MySQL，用来提供数据库服务。

• P指PHP，是动态网站的的一种开发语言。

LAMP是中小型动态网站的常见组合，虽然这些开放源代码程序本身并不是专门设计成同另几个程序一起工作的，但由于它们各自的特点和普遍性，使得这个组合在搭建动态网站这一领域开始流行起来。

3.11.2 PHP 简介

PHP：（Hypertext Preprocessor）超文本预处理器。

PHP是通用服务器端脚本编程语言，主要用于WEB开发实现动态WEB页面，也是最早实现将脚本嵌入HTML源码文档中的服务器端脚本语言之一。同时，PHP还提供了一个命令行接口，因此，其也可以在大多数系统上作为一个独立的SHELL来使用。Rasmus Lerdorf于1994年开始开发PHP，最初是一组被Rasmus Lerdorf称作"Personal Home PageTool"的Perl脚本，可以用于显示作者的简历并记录用户对其网站的访问。后来，Rasmus Lerdorf使用C语言将这些Perl脚本重写为CGI程序，还为其增加了运行Webforms的能力以及与数据库交互的特性，并将其重命名为"Personal Home Page/Forms Interpreter"或"PHP/FI"。此时，PHP/FI已经可以用于开发简单的动态WEB程序了，这即PHP1.0。1995年6月,RasmusLerdorf 把它的 PHP发布于comp.infosystems.www.authoring.cgi Usenet讨论组，从此PHP开始走进人们的视野。1997年，其2.0版本发布。

1997年，两名以色列程序员Zeev Suraski 和Andi Gutmans重写的PHP的分析器（parser)成为 PHP发展到3.0的基础，而且从此将PHP重命名为PHP:Hypertext Preprocessor。此后，这两名程序员开始重写整个PHP核心，并于1999年发布了Zend Engine1.0，这也意味着PHP 4.0的诞生。2004年7月，

ZendEngine 2.0发布，由此也将PHP带入了PHP5时代。PHP5包含了许多重要的新特性，如增强的面向对象编程的支持、支持PDO(PHP Data Objects）扩展机制以及一系列对PHP性能的改进。

Zend Engine是开源的、PHP脚本语言的解释器，它最早是由以色列理工学院（Technion）的学生AndiGutmans和Zeev Suraski 所开发，Zend也正是此二人名字的合称。后来两人联合创立了ZendTechnologies公司。

Zend Engine1.0于1999年随PHP4发布，由C语言开发且经过高度优化，并能够做为PHP的后端模块使用。Zend Engine为PHP提供了内存和资源管理的功能以及其它的一些标准服务，其高性能、可靠性和可扩展性在促进PHP成为一种流行的语言方面发挥了重要作用。Zend Engine的出现将PHP代码的处理过程分成了两个阶段：首先是分析PHP代码并将其转换为称作Zend opcode的二进制格式opcode(类似Java的字节码），并将其存储于内存中；第二阶段是使用ZendEngine去执行这些转换后的Opcode。

PHP各种版本官方支持时间

https://www.php.net/supported-versions.php

php常见配置项

expose_php=On #响应报文显示首部字段x-powered-by：PHP/x.y.z，暴露php版本，建议为off
max_execution_time=30 #最长执行时间30s
memory_limit=128M #生产不够，可调大
display_errors=off #调试使用，不要打开，否则可能暴露重要信息
display_startup_errors=off #建议关闭
post_max_size=8M #最大上传数据大小，生产可能调大，比下面项大
upload_max_filesize=2M #最大上传文件，生产可能要调大
max_file_uploads=20 #同时上传最多文件数
date.timezone=Asia/shanghai #指定时区
short_open_tag=On #支持短标签

3.11.3 实现博客项目

服务器配置

IP地址规划	作用	软件
192.168.108.100	提供WEB服务，PHP动态解析	Apache，PHP
192.168.108.101	提供数据库服务	MySQL

WordPress

WordPress是使用PHP语言开发的博客平台，用户可以在支持PHP和MySQL数据库的服务器上架设属于自己的网站。也可以把WordPress当作一个内容管理系统（CMS）来使用。

官方网站

https://cn.wordpress.org/

具体实现

[root@localhost ~ 11:39:24]# hostnamectl set-hostname web

#在100上安装apapche和PHP
[root@web ~ 11:41:56]# yum -y install httpd php php-mysqlnd php-json php-gd php-xml php-mbstring php-zip unzip

[root@web ~ 11:42:21]# php -v
PHP 7.2.24 (cli) (built: Oct 22 2019 08:28:36) ( NTS )
Copyright (c) 1997-2018 The PHP Group
Zend Engine v3.2.0, Copyright (c) 1998-2018 Zend Technologies

#关闭防火墙
[root@web ~ 11:46:55]# systemctl disable --now firewalld
Removed /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.

#启动WEB服务
[root@web ~ 11:47:02]# systemctl start httpd.service

#添加php测试页面
[root@web ~ 11:47:31]# yum install -y vim
[root@web ~ 11:47:51]# vim /var/www/html/test.php
[root@web ~ 11:48:19]# cat /var/www/html/test.php
<?php
phpinfo();

通过浏览器访问

#下载wordpress 源码
[root@web ~ 11:48:22]# cd /var/www/html
[root@web html 11:49:41]# yum install wget -y
[root@web html 11:50:03]# wget https://cn.wordpress.org/latest-zh_CN.zip
--2025-12-08 11:50:17--  https://cn.wordpress.org/latest-zh_CN.zip
Resolving cn.wordpress.org (cn.wordpress.org)... 198.143.164.252, 2607:f978:5:8002::c68f:a4fc
Connecting to cn.wordpress.org (cn.wordpress.org)|198.143.164.252|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 36105878 (34M) [application/zip]
Saving to: 'latest-zh_CN.zip'

latest-zh_CN.zip      100%[=========================>]  34.43M   528KB/s    in 77s

2025-12-08 11:51:35 (459 KB/s) - 'latest-zh_CN.zip' saved [36105878/36105878]

[root@web html 11:51:35]# ls
latest-zh_CN.zip  test.php
[root@web html 12:22:11]# unzip latest-zh_CN.zip

[root@web html 12:22:18]# ls
latest-zh_CN.zip  test.php  wordpress

#修改属主属组
[root@web html 12:22:27]# chown -R apache.apache wordpress/

#切换到101节点，创建数据库
[root@localhost ~ 11:41:20]# mysql -uroot -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 8
Server version: 8.0.26 Source distribution

Copyright (c) 2000, 2021, Oracle and/or its affiliates.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> create user 'wordpress'@'192.168.108.%' identified by '123456';
Query OK, 0 rows affected (0.01 sec)

mysql> grant all on wordpress.* to 'wordpress'@'192.168.108.%';
Query OK, 0 rows affected (0.00 sec)

mysql>

为项目配置域名

#在web服务器上配置域名指向的目录
[root@web html 12:27:31]# vim /etc/httpd/conf.d/blog.dyx.cloud.conf

#重启httpd
[root@web html 12:30:19]# systemctl restart httpd
[root@web html 12:30:22]# cat /etc/httpd/conf.d/blog.dyx.cloud.conf
<VirtualHost *:80>
  ServerName blog.dyx.cloud
  DocumentRoot "/var/www/html/wordpress"
  <Directory "/var/www/html/wordpress">
    AllowOverride all
    Order allow,deny
    Allow from all
    </Directory>
</VirtualHost>

#在C:\windows\System32\drivers\etc\hosts添中如下行
192.168.108.100 blog.dyx.cloud

在页面上填写相关配置

4. mysql 5.x源码安装

环境准备：

使用CentOS-7-template模板克隆mysql01

#设置主机名
[root@localhost ~]# hostnamectl set-hostname mysql01

#关闭防火墙
[root@localhost ~]# systemctl disable firewalld.service --now
systemctl disable firewalld.service --now
Removed symlink /etc/systemd/system/multi-user.target.wants/firewalld.service.
Removed symlink /etc/systemd/system/dbus-org.fedoraproject.FirewallD1.service.

mysql5.7稳定版安装

#安装依赖包，ncurses（基础运行时库） ncurses-devel（可操作终端）bison（解析语法） cmake（源码编译工具） gcc，gcc-c++（编译器）
[root@localhost ~]# yum -y install ncurses ncurses-devel bison cmake gcc gcc-c++

#配置程序用户（不允许终端登录）
[root@localhost ~]# useradd -s /sbin/nologin mysql

#解压mysql和boost包到指定目录，boost是支持mysql底层c++运行的仓库
[root@mysql01 ~]# ls
anaconda-ks.cfg  Documents  initial-setup-ks.cfg  Pictures  Templates
Desktop          Downloads  Music                 Public    Videos
[root@mysql01 ~]# ls
anaconda-ks.cfg      Documents             Music                Public
boost_1_59_0.tar.gz  Downloads             mysql-5.7.17.tar.gz  Templates
Desktop              initial-setup-ks.cfg  Pictures             Videos

[root@mysql01 ~]# tar zxvf mysql-5.7.17.tar.gz -C /opt/

[root@mysql01 ~]# tar zxvf boost_1_59_0.tar.gz -C /usr/local/

[root@mysql01 mysql-5.7.17]# cd /usr/local/
[root@mysql01 local]# mv boost_1_59_0/ boost

#配置安装环境
[root@mysql01 mysql-5.7.17]# cd /opt/mysql-5.7.17/     

[root@mysql01 mysql-5.7.17]# cmake \
-DCMAKE_INSTALL_PREFIX=/usr/local/mysql \
-DMYSQL_UNIX_ADDR=/usr/local/mysql/mysql.sock -DSYSCONFDIR=/etc \
-DSYSTEMD_PID_DIR=/usr/local/mysql -DDEFAULT_CHARSET=utf8 \
-DDEFAULT_COLLATION=utf8_general_ci -DWITH_INNOBASE_STORAGE_ENGINE=1 \
-DWITH_ARCHIVE_STORAGE_ENGINE=1 -DWITH_BLACKHOLE_STORAGE_ENGINE=1 \
-DWITH_PERFSCHEMA_STORAGE_ENGINE=1 -DMYSQL_DATADIR=/usr/local/mysql/data \
-DWITH_BOOST=/usr/local/boost \
-DWITH_SYSTEMD=1


#注释 
cmake \
-DCMAKE_INSTALL_PREFIX=/usr/local/mysql \ #安装路径
-DMYSQL_UNIX_ADDR=/usr/local/mysql/mysql.sock \ #客户端连服务的通讯文件
-DSYSCONFDIR=/etc \ #mysql的配置文件
-DSYSTEMD_PID_DIR=/usr/local/mysql \ #pid进程文件存放位置
-DDEFAULT_CHARSET=utf8  \	#字符集格式
-DDEFAULT_COLLATION=utf8_general_ci \	#字符集位置
-DWITH_INNOBASE_STORAGE_ENGINE=1 \	#开启支持的存储引擎
-DWITH_ARCHIVE_STORAGE_ENGINE=1 \
-DWITH_BLACKHOLE_STORAGE_ENGINE=1 \
-DWITH_PERFSCHEMA_STORAGE_ENGINE=1 \
-DMYSQL_DATADIR=/usr/local/mysql/data \  #数据存放位置
-DWITH_BOOST=/usr/local/boost \		#底层的c++支持库位置
-DWITH_SYSTEMD=1	#id号
------注意：如果在CMAKE的过程中有报错，当报错解决后，需要把源码目录中的CMakeCache.txt文件删除，然后再重新CMAKE，否则错误依旧------------

#编译和安装
[root@mysql01 mysql-5.7.17]# make && make install

#递归配置目录所属主和组
[root@mysql01 mysql-5.7.17]# chown -R mysql.mysql /usr/local/mysql/

#编辑mysql的配置文件，直接全替换
[root@mysql01 mysql-5.7.17]# vim /etc/my.cnf
[root@mysql01 mysql-5.7.17]# cat /etc/my.cnf
[client]
port = 3306
default-character-set=utf8
socket = /usr/local/mysql/mysql.sock

[mysql]
port = 3306
default-character-set=utf8
socket = /usr/local/mysql/mysql.sock

[mysqld]
user = mysql
basedir = /usr/local/mysql
datadir = /usr/local/mysql/data
port = 3306
character_set_server=utf8
pid-file = /usr/local/mysql/mysqld.pid
socket = /usr/local/mysql/mysql.sock
server-id = 1

sql_mode=NO_ENGINE_SUBSTITUTION,STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_AUTO_VALUE_ON_ZERO,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,PIPES_AS_CONCAT,ANSI_QUOTES

#配置文件所属主和组
[root@mysql01 mysql-5.7.17]# chown mysql:mysql /etc/my.cnf

#配置环境变量
[root@mysql01 mysql-5.7.17]# echo 'PATH=/usr/local/mysql/bin:/usr/local/mysql/lib:$PATH' >> /etc/profile
[root@mysql01 mysql-5.7.17]# echo 'export PATH' >> /etc/profile

#加载修改过的配置
[root@mysql01 mysql-5.7.17]# source /etc/profile

#数据库初始化
[root@mysql01 mysql-5.7.17]# cd /usr/local/mysql/
[root@mysql01 mysql]# bin/mysqld \
 --initialize-insecure \
 --user=mysql \
 --basedir=/usr/local/mysql \
 --datadir=/usr/local/mysql/data

2025-12-08T08:16:18.818356Z 0 [Warning] TIMESTAMP with implicit DEFAULT value is deprecated. Please use --explicit_defaults_for_timestamp server option (see documentation for more details).
2025-12-08T08:16:18.937592Z 0 [Warning] InnoDB: New log files created, LSN=45790
2025-12-08T08:16:18.957216Z 0 [Warning] InnoDB: Creating foreign key constraint system tables.
2025-12-08T08:16:19.012791Z 0 [Warning] No existing UUID has been found, so we assume that this is the first time that this server has been started. Generating a new UUID: 2c867e6e-d40e-11f0-95b6-000c29c02be2.
2025-12-08T08:16:19.013555Z 0 [Warning] Gtid table is not ready to be used. Table 'mysql.gtid_executed' cannot be opened.
2025-12-08T08:16:19.013967Z 1 [Warning] root@localhost is created with an empty password ! Please consider switching off the --initialize-insecure option.

[root@mysql01 mysql]# cp /usr/local/mysql/usr/lib/systemd/system/mysqld.service /usr/lib/systemd/system/
[root@mysql01 mysql]# systemctl daemon-reload
[root@mysql01 mysql]# systemctl start mysqld
[root@mysql01 mysql]# netstat -anpt | grep 3306
tcp6       0      0 :::3306                 :::*                    LISTEN      11779/mysqld
[root@mysql01 mysql]# systemctl enable mtsqld
Failed to execute operation: No such file or directory
[root@mysql01 mysql]# systemctl enable mysqld
Created symlink from /etc/systemd/system/multi-user.target.wants/mysqld.service to /usr/lib/systemd/system/mysqld.service.

#给root账号设置密码为huawei，提示输入的是原始密码（密码为空）。
[root@mysql01 mysql]# mysqladmin -u root -p password "123"
Enter password:
mysqladmin: [Warning] Using a password on the command line interface can be insecure.
Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.

#登录mysql
[root@mysql01 mysql]# mysql -u root -p
Enter password:
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.17 Source distribution

Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

#授权远程登录
mysql> grant all privileges on *.* to 'root'@'%' identified by 'huawei' with grant option;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> quit
Bye
[root@mysql01 mysql]# poweroff

做完，拍摄快照

基础SQL-DDL语句

• 查询数据库

  [root@mysql01 ~]# mysql -uroot -p123

ss'@'192.168.108.%' identified by '123456';

Query OK, 0 rows affected (0.01 sec)

mysql> grant all on wordpress.* to 'wordpress'@'192.168.108.%';

Query OK, 0 rows affected (0.00 sec)

mysql>

为项目配置域名

```bash
#在web服务器上配置域名指向的目录
[root@web html 12:27:31]# vim /etc/httpd/conf.d/blog.dyx.cloud.conf

#重启httpd
[root@web html 12:30:19]# systemctl restart httpd
[root@web html 12:30:22]# cat /etc/httpd/conf.d/blog.dyx.cloud.conf
<VirtualHost *:80>
  ServerName blog.dyx.cloud
  DocumentRoot "/var/www/html/wordpress"
  <Directory "/var/www/html/wordpress">
    AllowOverride all
    Order allow,deny
    Allow from all
    </Directory>
</VirtualHost>

#在C:\windows\System32\drivers\etc\hosts添中如下行
192.168.108.100 blog.dyx.cloud

在页面上填写相关配置