数据库概述、部署MySQL服务、必备命令、密码管理、安装图形软件、SELECT语法 、筛选条件

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NSD DBA DAY01

  1. 案例1:构建MySQL服务器
  2. 案例2:密码管理
  3. 案例3:安装图形软件
  4. 案例4:筛选条件

1 案例1:构建MySQL服务器

1.1 问题

  1. 在IP地址192.168.88.50主机和192.168.88.51主机上部署mysql服务
  2. 练习必备命令的使用

1.2 方案

准备2台虚拟机,要求如下:

表-1

配置yum源、关闭selinux和防火墙,如果忘记了请自行补习前边课程的知识或查看今天讲课的PPT,谢谢!!!

1.3 步骤

实现此案例需要按照如下步骤进行。

步骤一:安装软件

命令操作如下所示:

mysql-server 提供服务软件

mysql 提供命令软件

复制代码
  1. [root@mysql50 ~]# yum -y install mysql-server mysql //安装提供服务和命令软件
  2. //软件已安装
  3. [root@mysql50 ~]# rpm -q mysql-server mysql
  4. mysql-server-8.0.26-1.module+el8.4.0+652+6de068a7.x86_64
  5. mysql-8.0.26-1.module+el8.4.0+652+6de068a7.x86_64
  6. [root@mysql50 ~]#
  7. [root@mysql50 ~]# rpm -qi mysql-server //查看软件信息
  8. Name : mysql-server
  9. Version : 8.0.26
  10. Release : 1.module+el8.4.0+652+6de068a7
  11. Architecture: x86_64
  12. Install Date: 2023年03月13日 星期一 12时09分38秒
  13. Group : Unspecified
  14. Size : 126674945
  15. License : GPLv2 with exceptions and LGPLv2 and BSD
  16. Signature : RSA/SHA256, 2021年09月22日 星期三 07时27分14秒, Key ID 15af5dac6d745a60
  17. Source RPM : mysql-8.0.26-1.module+el8.4.0+652+6de068a7.src.rpm
  18. Build Date : 2021年09月22日 星期三 07时06分32秒
  19. Build Host : ord1-prod-x86build005.svc.aws.rockylinux.org
  20. Relocations : (not relocatable)
  21. Packager : infrastructure@rockylinux.org
  22. Vendor : Rocky
  23. URL : http://www.mysql.com
  24. Summary : The MySQL server and related files
  25. Description :
  26. MySQL is a multi-user, multi-threaded SQL database server. MySQL is a
  27. client/server implementation consisting of a server daemon (mysqld)
  28. and many different client programs and libraries. This package contains
  29. the MySQL server and some accompanying files and directories.
  30. [root@mysql50 ~]# systemctl start mysqld //启动服务
  31. [root@mysql50 ~]# systemctl enable mysqld //开机运行
  32. [root@mysql50 ~]# systemctl enable mysqld //设置服务开机运行
  33. Created symlink /etc/systemd/system/multi-user.target.wants/mysqld.service → /usr/lib/systemd/system/mysqld.service.

步骤二:查看端口号和进程名

命令操作如下所示:

复制代码
  1. [root@mysql50 ~]# ps -C mysqld //查看进程
  2. PID TTY TIME CMD
  3. 21912 ? 00:00:00 mysqld
  4. [root@mysql50 ~]#
  5. [root@mysql50 ~]# ss -utnlp | grep 3306 查看端口
  6. tcp LISTEN 0 70 *:33060 *:* users:(("mysqld",pid=21912,fd=22))
  7. tcp LISTEN 0 128 *:3306 *:* users:(("mysqld",pid=21912,fd=25))
  8. [root@mysql50 ~]#
  9. [root@mysql50 ~]# netstat -utnlp | grep mysqld //仅查看mysqld进程
  10. tcp6 0 0 :::33060 :::* LISTEN 21912/mysqld
  11. tcp6 0 0 :::3306 :::* LISTEN 21912/mysqld
  12. [root@mysql50 ~]#

说明:

MySQL 8中的3306端口是MySQL服务默认使用的端口,主要用于建立客户端与MySQL服务器之间的连接。

MySQL 8中的33060端口是MySQL Shell默认使用的管理端口,主要用于执行各种数据库管理任务。远程管理MySQL服务器:使用MySQL Shell连接到MySQL服务,并在远程管理控制台上执行各种数据库管理操作,例如创建、删除、备份和恢复数据库等。

步骤三:连接服务。

说明: 数据库管理员本机登陆默认没有密码

命令操作如下所示:

复制代码
  1. [root@mysql50 ~]# mysql //连接服务
  2. Welcome to the MySQL monitor. Commands end with ; or \g.
  3. Your MySQL connection id is 8
  4. Server version: 8.0.26 Source distribution
  5. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
  6. Oracle is a registered trademark of Oracle Corporation and/or its
  7. affiliates. Other names may be trademarks of their respective
  8. owners.
  9. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  10. mysql> 登陆后的提示符
  11. mysql> exit //断开连接
  12. Bye
  13. [root@mysql50 ~]#

步骤四:配置第2台数据库服务器MySQL51。

命令操作如下所示:

复制代码
  1. [root@mysql51 ~]# yum -y install mysql-server mysql
  2. [root@mysql51 ~]# systemctl start mysqld
  3. [root@mysql51 ~]# systemctl enable mysqld
  4. [root@mysql51 ~]# mysql
  5. mysql> exit
  6. Bye
  7. [root@mysql51 ~]#

步骤五:练习必备命令的使用(在mysql50主机完成练习)

命令操作如下所示:

复制代码
  1. mysql> select version() ; //查看数据库软件版本
  2. +-----------+
  3. | version() |
  4. +-----------+
  5. | 8.0.26 |
  6. +-----------+
  7. 1 row in set (0.00 sec)
  8. mysql> select user() ; //查看登陆的用户和客户端地址
  9. +----------------+
  10. | user() |
  11. +----------------+
  12. | root@localhost | 管理员root本机登陆
  13. +----------------+
  14. 1 row in set (0.00 sec)
  15. mysql> show databases; //查看已有的库
  16. +--------------------+
  17. | Database |
  18. +--------------------+
  19. | information_schema |
  20. | mysql |
  21. | performance_schema |
  22. | sys |
  23. +--------------------+
  24. 4 rows in set (0.00 sec)
  25. mysql>

说明:

默认4个库 不可以删除,存储的是 服务运行时加载的不同功能的程序和数据。

information_schema:是MySQL数据库提供的一个虚拟的数据库,存储了MySQL数据库中的相关信息,比如数据库、表、列、索引、权限、角色等信息。它并不存储实际的数据,而是提供了一些视图和存储过程,用于查询和管理数据库的元数据信息。

mysql:存储了MySQL服务器的系统配置、用户、账号和权限信息等。它是MySQL数据库最基本的库,存储了MySQL服务器的核心信息。

performance_schema:存储了MySQL数据库的性能指标、事件和统计信息等数据,可以用于性能分析和优化。

sys:是MySQL 8.0引入的一个新库,它基于information_schema和performance_schema视图,提供了更方便、更直观的方式来查询和管理MySQL数据库的元数据和性能数据。

复制代码
  1. mysql> select database(); //查看当前在那个库里 null 表示没有在任何库里
  2. +------------+
  3. | database() |
  4. +------------+
  5. | NULL |
  6. +------------+
  7. 1 row in set (0.00 sec)
  8. mysql> use mysql ; //切换到mysql库
  9. mysql> select database(); // 再次显示所在的库
  10. +------------+
  11. | database() |
  12. +------------+
  13. | mysql |
  14. +------------+
  15. 1 row in set (0.00 sec)
  16. mysql> show tables; //显示库里已有的表
  17. +------------------------------------------------------+
  18. | Tables_in_mysql |
  19. +------------------------------------------------------+
  20. | columns_priv |
  21. | component |
  22. | db |
  23. | default_roles |
  24. | engine_cost |
  25. | func |
  26. | general_log |
  27. | global_grants |
  28. | gtid_executed |
  29. | help_category |
  30. | help_keyword |
  31. | help_relation |
  32. | help_topic |
  33. | innodb_index_stats |
  34. | innodb_table_stats |
  35. | password_history |
  36. | plugin |
  37. | procs_priv |
  38. | proxies_priv |
  39. | replication_asynchronous_connection_failover |
  40. | replication_asynchronous_connection_failover_managed |
  41. | replication_group_configuration_version |
  42. | replication_group_member_actions |
  43. | role_edges |
  44. | server_cost |
  45. | servers |
  46. | slave_master_info |
  47. | slave_relay_log_info |
  48. | slave_worker_info |
  49. | slow_log |
  50. | tables_priv |
  51. | time_zone |
  52. | time_zone_leap_second |
  53. | time_zone_name |
  54. | time_zone_transition |
  55. | time_zone_transition_type |
  56. | user |
  57. +------------------------------------------------------+
  58. 37 rows in set (0.00 sec)
  59. mysql> exit ; 断开连接
  60. Bye
  61. [root@mysql50 ~]#

2 案例2:密码管理

2.1 问题

1) 在192.168.88.50主机做如下练习:

  1. 设置root密码为tarena
  2. 修改root密码为123qqq...A
  3. 破解root密码为NSD2023...a

2.2 步骤

实现此案例需要按照如下步骤进行。

步骤一:设置root密码为tarena

命令操作如下所示:

2行输出是警告而已不用关心

复制代码
  1. [root@mysql50 ~]# mysqladmin -uroot -p password "tarena"
  2. Enter password: //敲回车
  3. mysqladmin: [Warning] Using a password on the command line interface can be insecure.
  4. Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.
  5. [root@mysql50 ~]# mysql //无密码连接被拒绝
  6. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
  7. [root@mysql50 ~]#
  8. [root@mysql50 ~]# mysql -uroot --ptarena //连接时输入密码
  9. mysql: [Warning] Using a password on the command line interface can be insecure.
  10. Welcome to the MySQL monitor. Commands end with ; or \g.
  11. Your MySQL connection id is 14
  12. Server version: 8.0.26 Source distribution
  13. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
  14. Oracle is a registered trademark of Oracle Corporation and/or its
  15. affiliates. Other names may be trademarks of their respective
  16. owners.
  17. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  18. mysql> 登陆成功

步骤二:修改root密码为123qqq...A

命令操作如下所示:

复制代码
  1. [root@mysql50 ~]# mysqladmin -uroot -ptarena password "123qqq...A" //修改密码
  2. mysqladmin: [Warning] Using a password on the command line interface can be insecure.
  3. Warning: Since password will be sent to server in plain text, use ssl connection to ensure password safety.
  4. [root@mysql50 ~]# mysql -uroot --ptarena //旧密码无法登陆
  5. mysql: [Warning] Using a password on the command line interface can be insecure.
  6. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
  7. [root@mysql50 ~]# mysql -uroot -p123qqq...A //新密码登陆
  8. mysql: [Warning] Using a password on the command line interface can be insecure.
  9. Welcome to the MySQL monitor. Commands end with ; or \g.
  10. Your MySQL connection id is 18
  11. Server version: 8.0.26 Source distribution
  12. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
  13. Oracle is a registered trademark of Oracle Corporation and/or its
  14. affiliates. Other names may be trademarks of their respective
  15. owners.
  16. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  17. mysql> 登陆成功

步骤三:破解root密码为NSD2023...a

说明:在mysql50主机做此练习

命令操作如下所示:

复制代码
  1. [root@mysql50 ~]# mysql -uroot -pNSD2023...a //破解前登陆失败
  2. mysql: [Warning] Using a password on the command line interface can be insecure.
  3. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: YES)
  4. [root@mysql50 ~]# vim /etc/my.cnf.d/mysql-server.cnf //修改主配置文件
  5. [mysqld]
  6. skip-grant-tables //手动添加此行 作用登陆时不验证密码
  7. :wq
  8. [root@mysql50 ~]# systemctl restart mysqld //重启服务 作用让服务以新配置运行
  9. [root@mysql50 ~]# mysql //连接服务
  10. Welcome to the MySQL monitor. Commands end with ; or \g.
  11. Your MySQL connection id is 7
  12. Server version: 8.0.26 Source distribution
  13. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
  14. Oracle is a registered trademark of Oracle Corporation and/or its
  15. affiliates. Other names may be trademarks of their respective
  16. owners.
  17. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  18. //把mysql库下user表中 用户root的密码设置为无;
  19. mysql> update mysql.user set authentication_string="" where user="root";
  20. Query OK, 1 row affected (0.05 sec)
  21. Rows matched: 1 Changed: 1 Warnings: 0
  22. mysql> exit; 断开连接
  23. Bye
  24. [root@mysql50 ~]# vim /etc/my.cnf.d/mysql-server.cnf 编辑配置文件
  25. [mysqld]
  26. #skip-grant-tables //注释添加的行
  27. :wq
  28. [root@mysql50 ~]# systemctl restart mysqld //重启服务 作用让注释生效
  29. [root@localhost ~]# mysql 无密码登陆
  30. Welcome to the MySQL monitor. Commands end with ; or \g.
  31. Your MySQL connection id is 8
  32. Server version: 8.0.26 Source distribution
  33. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
  34. Oracle is a registered trademark of Oracle Corporation and/or its
  35. affiliates. Other names may be trademarks of their respective
  36. owners.
  37. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  38. //设置root用户本机登陆密码
  39. mysql> alter user root@"localhost" identified by "NSD2023...a";
  40. Query OK, 0 rows affected (0.00 sec)
  41. mysql> exit 断开连接
  42. Bye
  43. [root@localhost ~]# mysql 不输密码无法登陆
  44. ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
  45. [root@localhost ~]# mysql -uroot -pNSD2023...a 使用破解的密码登陆
  46. mysql: [Warning] Using a password on the command line interface can be insecure.
  47. Welcome to the MySQL monitor. Commands end with ; or \g.
  48. Your MySQL connection id is 10
  49. Server version: 8.0.26 Source distribution
  50. Copyright (c) 2000, 2021, Oracle and/or its affiliates.
  51. Oracle is a registered trademark of Oracle Corporation and/or its
  52. affiliates. Other names may be trademarks of their respective
  53. owners.
  54. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
  55. mysql>
  56. mysql> 登陆成功
  57. mysql> show databases; 查看已有的库
  58. +--------------------+
  59. | Database |
  60. +--------------------+
  61. | information_schema |
  62. | mysql |
  63. | performance_schema |
  64. | sys |
  65. +--------------------+
  66. 4 rows in set (0.01 sec)

3 案例3:安装图形软件

3.1 问题

  • 在IP地址192.168.88.50主机安装phpmyadmin软件
  • 客户端通过访问phpmyadmin软件管理数据库

3.2 方案

把用到的软件拷贝的虚拟机mysql50里

在mysql50主机,首先配置运行环境LNP,然后安装phpmyadmin软件,最后打开真机的浏览器输入phpmyadmin的网址访问。

3.3 步骤

实现此案例需要按照如下步骤进行。

步骤一:部署运行环境LNP

命令操作如下所示:

复制代码
  1. gcc 源码包编译工具
  2. unzip 提供解压.zip 压缩包命令
  3. make 源码软件编译命令
  4. pcre-devel 支持正则表达式
  5. zlib-devel 提供数据压缩命令
  6. [root@mysql50 ~]# yum -y install gcc unzip make pcre-devel zlib-devel //安装依赖
  7. [root@mysql50 ~]# tar -xf nginx-1.22.1.tar.gz //解压源码
  8. [root@mysql50 ~]# cd nginx-1.22.1 //进源码目录
  9. [root@mysql50 nginx-1.22.1]# ./configure //配置
  10. [root@mysql50 nginx-1.22.1]# make && make install //编译并安装
  11. [root@mysql50 nginx-1.22.1]# ls /usr/local/nginx/ //查看安装目录
  12. conf html logs sbin
  13. [root@mysql50 nginx-1.22.1]# vim /usr/local/nginx/conf/nginx.conf //修改主配置文件
  14. 43 location / {
  15. 44 root html;
  16. 45 index index.php index.html index.htm; //添加php首页名
  17. 46 }
  18. 65 location ~ \.php$ { //访问.php的请求转给本机的9000端口
  19. 66 root html;
  20. 67 fastcgi_pass 127.0.0.1:9000;
  21. 68 fastcgi_index index.php;
  22. 69 #fastcgi_param SCRIPT_FILENAME /scripts$fastcgi_script_name;
  23. 70 include fastcgi.conf; //保存nginx变量文件
  24. 71 }
  25. :wq
  26. [root@mysql50 nginx-1.22.1]# /usr/local/nginx/sbin/nginx //启动服务
  27. [root@mysql50 nginx-1.22.1]# netstat -utnlp | grep 80 //查看端口
  28. tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN 42182/nginx: master
  29. [root@mysql50 nginx-1.22.1]#
  30. php 解释php代码
  31. php-devel php扩展包
  32. php-mysqlnd 连接mysql命令包
  33. php-json 支持json代码
  34. php-fpm 提供fpm服务
  35. [root@mysql50 ~]# yum -y install php php-devel php-mysqlnd php-json php-fpm //安装php软件
  36. [root@mysql50 ~]# vim /etc/php-fpm.d/www.conf //修改主配置文件
  37. 38 ;listen = /run/php-fpm/www.sock
  38. 39 listen = 127.0.0.1:9000 //非socket方式运行,不是必须的
  39. :wq
  40. [root@mysql50 ~]# systemctl start php-fpm //启动服务
  41. [root@mysql50 ~]# netstat -utnlp | grep 9000 //查看端口
  42. tcp 0 0 127.0.0.1:9000 0.0.0.0:* LISTEN 67251/php-fpm: mast
  43. [root@mysql50 ~]#
  44. [root@mysql50 ~]# vim /usr/local/nginx/html/test.php //编写php脚本
  45. <?php
  46. $name = "plj" ;
  47. echo $name ;
  48. echo "\n" ;
  49. ?>
  50. :wq
  51. [root@mysql50 ~]# curl http://localhost/test.php //访问脚本
  52. plj
  53. [root@mysql50 ~]#

步骤二:安装phpmyadmin软件

命令操作如下所示:

复制代码
  1. [root@mysql50 ~]# unzip phpMyAdmin-5.2.1-all-languages.zip //解压
  2. [root@mysql50 ~]# mv phpMyAdmin-5.2.1-all-languages /usr/local/nginx/html/phpmyadmin //移动并改名 ,为了便于访问
  3. [root@mysql50 ~]# cd /usr/local/nginx/html/phpmyadmin/ //进软件目录
  4. [root@mysql50 phpmyadmin]# cp config.sample.inc.php config.inc.php //创建主配置文件
  5. [root@mysql50 phpmyadmin]# vim config.inc.php //修改主配置文件
  6. //定义cookies验证码
  7. 16 $cfg['blowfish_secret'] = 'plj123'; /* YOU MUST FILL IN THIS FOR COOKIE AUTH! */
  8. //管理本机的数据库服务
  9. 30 cfg\['Servers'\]\[i]['host'] = 'localhost';
  10. :wq
  11. [root@mysql50 phpmyadmin]# setenforce 0 //关闭selinux
  12. [root@mysql50 phpmyadmin]# systemctl stop firewalld //关闭防火墙

步骤三:客户端访问

命令操作如下所示:

复制代码
  1. http://192.168.88.50/phpmyadmin 打开浏览器输入此网址 效果如图-1所示

图-1

说明:输入数据库管理员root 和 密码 成功后如图-2所示

4 案例4:筛选条件

4.1 问题

  1. 准备练习环境
  2. 练习数值比较
  3. 练习范围匹配
  4. 练习模糊匹配
  5. 练习正则匹配
  6. 练习逻辑比较
  7. 练习字符比较/空/非空
  8. 练习别名/去重/合并

4.2 方案

拷贝tarena.sql文件到mysql50主机里,然后使用tarena.sql创建练习使用的数据。

4.3 步骤

实现此案例需要按照如下步骤进行。

步骤一:准备练习环境

复制代码
  1. //拷贝tarena.sql 拷贝到 mysql50主机的/root 下
  2. [openeuler@server1 ~]$ scp /linux-soft/s3/tarena.sql root@192.168.88.50:/root/
  3. root@192.168.88.50's password:
  4. tarena.sql 100% 284KB 171.9MB/s 00:00
  5. //连接mysql50主机
  6. [openeuler@server1 ~]$ ssh root@192.168.88.50
  7. root@192.168.88.50's password:
  8. Last login: Tue May 23 10:59:57 2023 from 192.168.88.254
  9. //恢复数据
  10. [root@mysql50 ~]# mysql -uroot -pNSD2023...a < /root/tarena.sql
  11. mysql: [Warning] Using a password on the command line interface can be insecure.
  12. //连接服务
  13. [root@mysql50 ~]# mysql -uroot -pNSD2023...a
  14. mysql> show databases; //查看库
  15. +--------------------+
  16. | Database |
  17. +--------------------+
  18. | information_schema |
  19. | mysql |
  20. | performance_schema |
  21. | sys |
  22. | tarena | 恢复的库
  23. +--------------------+
  24. 5 rows in set (0.00 sec)
  25. mysql> use tarena; //进入库
  26. Reading table information for completion of table and column names
  27. You can turn off this feature to get a quicker startup with -A
  28. Database changed
  29. mysql> show tables; //查看表
  30. +------------------+
  31. | Tables_in_tarena |
  32. +------------------+
  33. | departments | 部门表
  34. | employees | 员工表
  35. | salary | 工资表
  36. | user | 用户表
  37. +------------------+
  38. 4 rows in set (0.00 sec)

使用user 表做查询练习

user表里存储的是 系统用户信息 就是 /etc/passwd 文件的内容

复制代码
  1. mysql> desc tarena.user; //查看表头
  2. +----------+-------------+------+-----+---------+----------------+
  3. | Field | Type | Null | Key | Default | Extra |
  4. +----------+-------------+------+-----+---------+----------------+
  5. | id | int(11) | NO | PRI | NULL | auto_increment |行号
  6. | name | char(20) | YES | | NULL | |用户名
  7. | password | char(1) | YES | | NULL | |密码占位符
  8. | uid | int(11) | YES | | NULL | | uid号
  9. | gid | int(11) | YES | | NULL | | gid号
  10. | comment | varchar(50) | YES | | NULL | | 描述信息
  11. | homedir | varchar(80) | YES | | NULL | | 家目录
  12. | shell | char(30) | YES | | NULL | | 解释器
  13. +----------+-------------+------+-----+---------+----------------+
  14. 8 rows in set (0.00 sec)

select命令格式演示

语法格式1 SELECT 字段列表 FROM 库名.表名;

语法格式2 SELECT 字段列表 FROM 库名.表名 where 筛选条件;

复制代码
  1. mysql> select name from tarena.user; //查看一个表头
  2. mysql> select name ,uid from tarena.user; //查看多个表头
  3. mysql> select * from tarena.user; //查看所有表头

加筛选条件

复制代码
  1. mysql> select * from tarena.user where name = "root"; //查找root用户信息
  2. +----+------+----------+------+------+---------+---------+-----------+
  3. | id | name | password | uid | gid | comment | homedir | shell |
  4. +----+------+----------+------+------+---------+---------+-----------+
  5. | 1 | root | x | 0 | 0 | root | /root | /bin/bash |
  6. +----+------+----------+------+------+---------+---------+-----------+
  7. 1 row in set (0.00 sec)
  8. mysql>
  9. mysql> select * from tarena.user where id = 2 ; //查找第2行用户信息
  10. +----+------+----------+------+------+---------+---------+--------------+
  11. | id | name | password | uid | gid | comment | homedir | shell |
  12. +----+------+----------+------+------+---------+---------+--------------+
  13. | 2 | bin | x | 1 | 1 | bin | /bin | /sbin/nologin |
  14. +----+------+----------+------+------+---------+---------+--------------+
  15. 1 row in set (0.00 sec)

步骤二:练习数值比较

比较符号:

= != > >= < <=

相等 不相等 大于 大于等于 小于 小于等于

符号两边要是数字或数值类型的表头 符号左边与符号右边做比较

复制代码
  1. //查看第3行的行号、用户名、uid、gid 四个表头的值
  2. mysql> select id,name,uid,gid from tarena.user where id = 3;
  3. +----+--------+------+------+
  4. | id | name | uid | gid |
  5. +----+--------+------+------+
  6. | 3 | daemon | 2 | 2 |
  7. +----+--------+------+------+
  8. 1 row in set (0.00 sec)
  9. //查看前2行的行号用户名、uid、gid 四个表头的值
  10. mysql> select id,name,uid,gid from tarena.user where id < 3;
  11. +----+------+------+------+
  12. | id | name | uid | gid |
  13. +----+------+------+------+
  14. | 1 | root | 0 | 0 |
  15. | 2 | bin | 1 | 1 |
  16. +----+------+------+------+
  17. 2 rows in set (0.00 sec)
  18. //查看前3行的行号、用户名、uid、gid 四个表头的值
  19. mysql> select id,name,uid,gid from tarena.user where id <= 3;
  20. +----+--------+------+------+
  21. | id | name | uid | gid |
  22. +----+--------+------+------+
  23. | 1 | root | 0 | 0 |
  24. | 2 | bin | 1 | 1 |
  25. | 3 | daemon | 2 | 2 |
  26. +----+--------+------+------+
  27. 3 rows in set (0.00 sec)
  28. //查看前uid号大于6000的行号、用户名、uid、gid 四个表头的值
  29. mysql> select id,name,uid,gid from tarena.user where uid > 6000;
  30. +----+-----------+-------+-------+
  31. | id | name | uid | gid |
  32. +----+-----------+-------+-------+
  33. | 22 | nfsnobody | 65534 | 65534 |
  34. +----+-----------+-------+-------+
  35. 1 row in set (0.00 sec)
  36. //查看前uid号大于等于1000的行号、用户名、uid、gid 四个表头的值
  37. mysql> select id,name,uid,gid from tarena.user where uid >= 1000;
  38. +----+-----------+-------+-------+
  39. | id | name | uid | gid |
  40. +----+-----------+-------+-------+
  41. | 22 | nfsnobody | 65534 | 65534 |
  42. | 24 | plj | 1000 | 1000 |
  43. +----+-----------+-------+-------+
  44. 2 rows in set (0.00 sec)
  45. //查看uid号和gid号相同的行 仅显示行号、用户名、uid、gid 四个表头的值
  46. mysql> select id,name,uid,gid from tarena.user where uid = gid;
  47. +----+-----------------+-------+-------+
  48. | id | name | uid | gid |
  49. +----+-----------------+-------+-------+
  50. | 1 | root | 0 | 0 |
  51. | 2 | bin | 1 | 1 |
  52. | 3 | daemon | 2 | 2 |
  53. | 13 | nobody | 99 | 99 |
  54. | 14 | systemd-network | 192 | 192 |
  55. | 15 | dbus | 81 | 81 |
  56. | 17 | sshd | 74 | 74 |
  57. | 18 | postfix | 89 | 89 |
  58. | 20 | rpc | 32 | 32 |
  59. | 21 | rpcuser | 29 | 29 |
  60. | 22 | nfsnobody | 65534 | 65534 |
  61. | 23 | haproxy | 188 | 188 |
  62. | 24 | plj | 1000 | 1000 |
  63. | 25 | apache | 48 | 48 |
  64. | 26 | mysql | 27 | 27 |
  65. +----+-----------------+-------+-------+
  66. 15 rows in set (0.00 sec)
  67. //查看uid号和gid号不一样的行 仅显示行号、用户名、uid、gid 四个表头的值
  68. mysql> select id,name,uid,gid from tarena.user where uid != gid;
  69. +----+----------+------+------+
  70. | id | name | uid | gid |
  71. +----+----------+------+------+
  72. | 4 | adm | 3 | 4 |
  73. | 5 | lp | 4 | 7 |
  74. | 6 | sync | 5 | 0 |
  75. | 7 | shutdown | 6 | 0 |
  76. | 8 | halt | 7 | 0 |
  77. | 9 | mail | 8 | 12 |
  78. | 10 | operator | 11 | 0 |
  79. | 11 | games | 12 | 100 |
  80. | 12 | ftp | 14 | 50 |
  81. | 16 | polkitd | 999 | 998 |
  82. | 19 | chrony | 998 | 996 |
  83. +----+----------+------+------+
  84. 11 rows in set (0.00 sec)
  85. mysql>

步骤三:练习范围匹配

in (值列表) //在...里

not in (值列表) //不在...里

between 数字1 and 数字2 //在...之间

命令操作如下所示:

复制代码
  1. //uid号表头的值 是 (1 , 3 , 5 , 7) 中的任意一个即可
  2. mysql> select name , uid from tarena.user where uid in (1 , 3 , 5 , 7);
  3. +------+------+
  4. | name | uid |
  5. +------+------+
  6. | bin | 1 |
  7. | adm | 3 |
  8. | sync | 5 |
  9. | halt | 7 |
  10. +------+------+
  11. //shell 表头的的值 不是 "/bin/bash"或"/sbin/nologin" 即可
  12. mysql> select name , shell from tarena.user where shell not in ("/bin/bash","/sbin/nologin");
  13. +----------+----------------+
  14. | name | shell |
  15. +----------+----------------+
  16. | sync | /bin/sync |
  17. | shutdown | /sbin/shutdown |
  18. | halt | /sbin/halt |
  19. | mysql | /bin/false |
  20. +----------+----------------+
  21. //id表头的值 在 10 到 20 之间即可 包括 10 和 20 本身
  22. mysql> select id , name , uid from tarena.user where id between 10 and 20 ;
  23. +----+-----------------+------+
  24. | id | name | uid |
  25. +----+-----------------+------+
  26. | 10 | operator | 11 |
  27. | 11 | games | 12 |
  28. | 12 | ftp | 14 |
  29. | 13 | nobody | 99 |
  30. | 14 | systemd-network | 192 |
  31. | 15 | dbus | 81 |
  32. | 16 | polkitd | 999 |
  33. | 17 | sshd | 74 |
  34. | 18 | postfix | 89 |
  35. | 19 | chrony | 998 |
  36. | 20 | rpc | 32 |
  37. +----+-----------------+------+
  38. 11 rows in set (0.00 sec)mysql>

步骤四:练习模糊匹配

where 字段名 like "表达式";

通配符

_ 表示 1个字符

% 表示零个或多个字符

命令操作如下所示:

复制代码
  1. //找名字必须是3个字符的 (没有空格挨着敲)
  2. mysql> select name from tarena.user where name like "___";
  3. +------+
  4. | name |
  5. +------+
  6. | bin |
  7. | adm |
  8. | ftp |
  9. | rpc |
  10. | plj |
  11. | bob |
  12. +------+
  13. 6 rows in set (0.00 sec)
  14. //找名字必须是4个字符的(没有空格挨着敲)
  15. mysql> select name from tarena.user where name like "_ _ _ _";
  16. +------+
  17. | name |
  18. +------+
  19. | root |
  20. | sync |
  21. | halt |
  22. | mail |
  23. | dbus |
  24. | sshd |
  25. | null |
  26. +------+
  27. 7 rows in set (0.00 sec)
  28. //找名字以字母a开头的(没有空格挨着敲)
  29. mysql> select name from tarena.user where name like "a%";
  30. //查找名字至少是4个字符的表达式
  31. mysql> select name from tarena.user where name like "%_ _ _ _%";(没有空格挨着敲)
  32. mysql> select name from tarena.user where name like "_ % _";(没有空格挨着敲)
  33. mysql> select name from tarena.user where name like "_ _ _ _%";(没有空格挨着敲)

步骤五:练习正则匹配

格式:select 字段名列表 from 库名.表名 where字段名 regexp '正则表达式';

回顾shell课程学过的元字符(正则符号)

^ 匹配行首

$ 匹配行尾

[] 匹配范围内任意一个

* 前边的表达式出现零次或多次

| 或者

. 任意一个字符

命令操作如下所示:

复制代码
  1. //添加有数字的名字
  2. insert into tarena.user(name)values("yaya9");
  3. insert into tarena.user(name)values("6yaya");
  4. insert into tarena.user(name)values("ya7ya");
  5. insert into tarena.user(name)values("yay8a");
  6. //查看名字里有数字的
  7. mysql> select name from tarena.user where name regexp "[0-9]";
  8. +-------+
  9. | name |
  10. +-------+
  11. | yaya9 |
  12. | 6yaya |
  13. | ya7ya |
  14. | yay8a |
  15. +-------+
  16. 4 rows in set (0.00 sec)
  17. //查看名字以数字开头
  18. mysql> select name from tarena.user where name regexp "^[0-9]";
  19. +-------+
  20. | name |
  21. +-------+
  22. | 6yaya |
  23. +-------+
  24. 1 row in set (0.00 sec)
  25. //查看名字以数字结尾
  26. mysql> select name from tarena.user where name regexp "[0-9]$";
  27. +-------+
  28. | name |
  29. +-------+
  30. | yaya9 |
  31. +-------+
  32. 1 row in set (0.00 sec)
  33. mysql>
  34. //查看名字以r开头
  35. mysql> select name from tarena.user where name regexp "^r";
  36. +---------+
  37. | name |
  38. +---------+
  39. | root |
  40. | rpc |
  41. | rpcuser |
  42. +---------+
  43. 3 rows in set (0.00 sec)
  44. //查看名字以t结尾
  45. mysql> select name from tarena.user where name regexp "t$";
  46. +------+
  47. | name |
  48. +------+
  49. | root |
  50. | halt |
  51. +------+
  52. 2 rows in set (0.00 sec)
  53. mysql>
  54. //查看名字以r开头或t结尾
  55. mysql> select name from tarena.user where name regexp "^r|t$";
  56. +---------+
  57. | name |
  58. +---------+
  59. | root |
  60. | halt |
  61. | rpc |
  62. | rpcuser |
  63. +---------+
  64. 4 rows in set (0.00 sec)
  65. //名字r开头t结尾
  66. mysql> select name from tarena.user where name regexp "^r.*t$";
  67. +------+
  68. | name |
  69. +------+
  70. | root |
  71. +------+
  72. 1 row in set (0.00 sec)
  73. mysql>

步骤六:练习逻辑比较

多个判断条件

逻辑与 and (&&) 多个判断条件必须同时成立

逻辑或 or (||) 多个判断条件其中某个条件成立即可

逻辑非 not (!) 取反

命令操作如下所示:

复制代码
  1. //逻辑非例子,查看解释器不是/bin/bash 的
  2. mysql> select name,shell from tarena.user where shell != "/bin/bash";
  3. //not 也是取反 要放在表达式的前边
  4. mysql> select name,shell from tarena.user where not shell = "/bin/bash";
  5. //id值不在 10 到 20 之间
  6. mysql> select id , name from tarena.user where not id between 10 and 20 ;
  7. //逻辑与 例子
  8. mysql> select name , uid from tarena.user where name="root" and uid = 1;
  9. Empty set (0.00 sec)
  10. mysql> select name , uid from tarena.user where name="root" and uid = 0;
  11. +------+------+
  12. | name | uid |
  13. +------+------+
  14. | root | 0 |
  15. +------+------+
  16. 1 row in set (0.00 sec)
  17. //逻辑或 例子
  18. mysql> select name , uid from tarena.user where name = "root" or name = "bin" or uid = 1;
  19. +------+------+
  20. | name | uid |
  21. +------+------+
  22. | root | 0 |
  23. | bin | 1 |
  24. +------+------+
  25. mysql>

() 提高优先级

复制代码
  1. mysql> select 2 + 3 * 5 ; //使用默认计算顺序 先乘除后加减
  2. +------------+
  3. | 2 + 3 * 5 |
  4. +------------+
  5. | 17 |
  6. +------------+
  7. 1 row in set (0.00 sec)
  8. mysql> select (2 + 3 ) * 5 ; //先加法再乘法
  9. +---------------+
  10. | (2 + 3 ) * 5 |
  11. +---------------+
  12. | 25 |
  13. +---------------+
  14. 1 row in set (0.00 sec)
  15. mysql>

逻辑匹配什么时候需要加()

逻辑与and 优先级高于逻辑或 or

如果在筛选条件里既有and 又有 or 默认先判断and 再判断or

复制代码
  1. //没加() 的查询结果
  2. select name , uid from tarena.user
  3. where name = "root" or name = "bin" and uid = 1 ;
  4. +------+------+
  5. | name | uid |
  6. +------+------+
  7. | root | 0 |
  8. | bin | 1 |
  9. +------+------+
  10. 2 rows in set (0.00 sec)
  11. //加()的查询结果
  12. select name , uid from tarena.user
  13. where (name = "root" or name = "bin") and uid = 1 ;
  14. +------+------+
  15. | name | uid |
  16. +------+------+
  17. | bin | 1 |
  18. +------+------+
  19. 1 row in set (0.00 sec)
  20. mysql>

步骤七:练习字符比较/空/非空

符号两边必须是字符 或字符类型的表头

= 相等比较

!= 不相等比较。

命令操作如下所示:

复制代码
  1. //查看表里是否有名字叫apache的用户
  2. mysql> select name from tarena.user where name="apache" ;
  3. +--------+
  4. | name |
  5. +--------+
  6. | apache |
  7. +--------+
  8. 1 row in set (0.00 sec)
  9. //输出解释器不是/bin/bash的用户名 及使用的解释器
  10. mysql> select name , shell from tarena.user where shell != "/bin/bash";
  11. +-----------------+----------------+
  12. | name | shell |
  13. +-----------------+----------------+
  14. | bin | /sbin/nologin |
  15. | daemon | /sbin/nologin |
  16. | adm | /sbin/nologin |
  17. | lp | /sbin/nologin |
  18. | sync | /bin/sync |
  19. | shutdown | /sbin/shutdown |
  20. | halt | /sbin/halt |
  21. | mail | /sbin/nologin |
  22. | operator | /sbin/nologin |
  23. | games | /sbin/nologin |
  24. | ftp | /sbin/nologin |
  25. | nobody | /sbin/nologin |
  26. | systemd-network | /sbin/nologin |
  27. | dbus | /sbin/nologin |
  28. | polkitd | /sbin/nologin |
  29. | sshd | /sbin/nologin |
  30. | postfix | /sbin/nologin |
  31. | chrony | /sbin/nologin |
  32. | rpc | /sbin/nologin |
  33. | rpcuser | /sbin/nologin |
  34. | nfsnobody | /sbin/nologin |
  35. | haproxy | /sbin/nologin |
  36. | apache | /sbin/nologin |
  37. | mysql | /bin/false |
  38. +-----------------+----------------+
  39. 24 rows in set (0.00 sec)
  40. mysql>

空 is null 表头下没有数据

非空 is not null 表头下有数据

mysql服务 使用关键字 null 或 NULL 表示表头没有数据

复制代码
  1. //添加新行 仅给行中的id 表头和name表头赋值
  2. mysql> insert into tarena.user(id,name) values(71,""); //零个字符
  3. mysql> insert into tarena.user(id,name) values(72,"null");//普通字母
  4. mysql> insert into tarena.user(id,name) values(73,NULL); //表示空
  5. mysql> insert into tarena.user(id,name) values(74,null); //表示空
  6. //查看id表头值大于等于70 的行 仅显示行中 id表头 和 name 表头的值
  7. mysql> select id , name from tarena.user where id >= 71;
  8. +----+------+
  9. | id | name |
  10. +----+------+
  11. | 71 | |
  12. | 72 | null |
  13. | 73 | NULL |
  14. | 74 | NULL |
  15. +----+------+
  16. //查看name 表头没有数据的行 仅显示行中id表头 和 naeme 表头的值
  17. mysql> select id , name from tarena.user where name is null;
  18. +----+------+
  19. | id | name |
  20. +----+------+
  21. | 28 | NULL |
  22. | 29 | NULL |
  23. | 73 | NULL |
  24. | 74 | NULL |
  25. +----+------+
  26. //查看name 表头是0个字符的行, 仅显示行中id表头 和 naeme 表头的值
  27. mysql> select id , name from tarena.user where name="";
  28. +----+------+
  29. | id | name |
  30. +----+------+
  31. | 71 | |
  32. +----+------+
  33. 1 row in set (0.00 sec)
  34. //查看name 表头值是null的行, 仅显示行中id表头 和 naeme 表头的值
  35. mysql> select id , name from tarena.user where name="null";
  36. +----+------+
  37. | id | name |
  38. +----+------+
  39. | 72 | null |
  40. +----+------+
  41. 1 row in set (0.00 sec)
  42. //查看name 表头有数据的行, 仅显示行中id表头 和 name 表头的值
  43. mysql> select id , name from tarena.user where name is not null;
  44. +----+-----------------+
  45. | id | name |
  46. +----+-----------------+
  47. | 1 | root |
  48. | 2 | bin |
  49. | 3 | daemon |
  50. | 4 | adm |
  51. | 5 | lp |
  52. ....
  53. ....
  54. | 27 | bob |
  55. | 71 | |
  56. | 72 | null |
  57. +----+-----------------+

步骤八:练习别名/去重/合并

命令操作如下所示:

复制代码
  1. //定义别名使用 as 或 空格
  2. mysql> select name , homedir from tarena.user;
  3. mysql> select name as 用户名 , homedir 家目录 from tarena.user;
  4. //拼接 concat()
  5. mysql> select concat(name,"-",uid) as 用户信息 from tarena.user where uid <= 5;
  6. +--------------+
  7. | 用户信息 |
  8. +--------------+
  9. | root-0 |
  10. | bin-1 |
  11. | daemon-2 |
  12. | adm-3 |
  13. | lp-4 |
  14. | sync-5 |
  15. +--------------+
  16. 6 rows in set (0.00 sec)
  17. //2列拼接
  18. mysql> select concat(name , "-" , uid) as 用户信息 from tarena.user where uid <= 5;
  19. //多列拼接
  20. mysql> select concat(name , "-" , uid , "-" , gid) as 用户信息 from tarena.user where uid <= 5;
  21. +--------------+
  22. | 用户信息 |
  23. +--------------+
  24. | root-0-0 |
  25. | bin-1-1 |
  26. | daemon-2-2 |
  27. | adm-3-4 |
  28. | lp-4-7 |
  29. | sync-5-0 |
  30. +--------------+

去重显示 distinct 字段名列表

复制代码
  1. //去重前输出
  2. mysql> select shell from tarena.user where shell in ("/bin/bash","/sbin/nologin") ;
  3. +---------------+
  4. | shell |
  5. +---------------+
  6. | /bin/bash |
  7. | /sbin/nologin |
  8. | /sbin/nologin |
  9. | /sbin/nologin |
  10. | /sbin/nologin |
  11. | /sbin/nologin |
  12. | /sbin/nologin |
  13. | /sbin/nologin |
  14. | /sbin/nologin |
  15. | /sbin/nologin |
  16. | /sbin/nologin |
  17. | /sbin/nologin |
  18. | /sbin/nologin |
  19. | /sbin/nologin |
  20. | /sbin/nologin |
  21. | /sbin/nologin |
  22. | /sbin/nologin |
  23. | /sbin/nologin |
  24. | /sbin/nologin |
  25. | /sbin/nologin |
  26. | /bin/bash |
  27. | /sbin/nologin |
  28. +---------------+
  29. 22 rows in set (0.00 sec)
  30. //去重后查看
  31. mysql> select distinct shell from tarena.user where shell in ("/bin/bash","/sbin/nologin") ;
  32. +---------------+
  33. | shell |
  34. +---------------+
  35. | /bin/bash |
  36. | /sbin/nologin |
  37. +---------------+
  38. 2 rows in set (0.01 sec)
  39. mysql>
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