mysql的安装
教程：
https://blog.csdn.net/lsrzhangmin/article/details/132492978?spm=100
1.2014.3001.5501
步骤：
1.官网下载或者wget,然后解压 -xf, 卸载mariadb yum -y install *mariadb
2. 确定 mysql-community-server 正常安装之后就可以开始配置
依次安装所需要的依赖包
3. 初始化 mysqld 服务 mysqld --initialize
4. 启动服务 systemctl start mysqld
注意：如果在启动时，出现以下的错误：
root@mysql1 \~# systemctl start mysqld
Job for mysqld.service failed because the control process exited with error code. See "systemctl status mysqld.service" and "journalctl -xe" for details.
这是因为/var/lib/mysql目录权限不够
修改权限并启动mysql:
root@mysql1 \~#setenforce 0
root@mysql1 \~# chown -R mysql:mysql /var/lib/mysql
root@mysql1 \~# chmod -R 777 /var/lib/mysql
root@mysql1 \~# systemctl start mysqld.service
root@mysql1 \~# ps -ef |grep mysq
mysql 2396 1 6 10:03 ? 00:00:00 /usr/sbin/mysqld
root 2443 1355 0 10:03 pts/0 00:00:00 grep --color=auto mysq
root@mysql1 \~# cd /var/lib/mysql
root@mysql1 mysql# ll
5. 添加开机启动列表 systecmctrl enable mysqld
6. 在 /var/log/mysqld.log 中找到初始密码，前后复制空格
cat /var/log/mysqld.log | grep password
7. 登录管理 mysql -uroot -p
将复制的密码粘贴到输入密码的区域，实现登录
8. 设置新的密码
在MySQL内将密码修改为root
mysql> ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY 'root';
数据库的管理
数据库的对象
1）数据库系统 DBMS
2）数据库 DB
3) 表 table
4) 记录 record
5) 字段 field
1.数据库的操作
创建库:
mysql> create database test charset utf8;
Query OK, 1 row affected, 1 warning (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
| test |
+--------------------+
5 rows in set (0.00 sec)
删除库:
mysql> drop database test;
Query OK, 0 rows affected (0.00 sec)
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.01 sec)
查看库:
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
4 rows in set (0.01 sec)
2.表的操作
选择库：
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
查看表：
mysql> show tables;
mysql> use test;
Database changed
mysql> show tables;
Empty set (0.00 sec)
创建表：
语法： create table 表名();
删除表：
drop table 表名；
新增列：在password后加一列
mysql> ALTER TABLE `test`.`user`
-> ADD COLUMN `realname` VARCHAR(45) NULL AFTER `password`;
Query OK, 0 rows affected (0.04 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> describe user; //查看表结构
+----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+----------------+
| id | int | NO | PRI | NULL | auto_increment |
| username | varchar(45) | NO | UNI | NULL | |
| password | varchar(45) | NO | | NULL | |
| realname | varchar(45) | YES | | NULL | |
+----------+-------------+------+-----+---------+----------------+
4 rows in set (0.01 sec)
修改列名：修改realname列名为zsxm
mysql> ALTER TABLE `test`.`user`
-> CHANGE COLUMN `realname` `zsxm` VARCHAR(45) NULL DEFAULT NULL ;
Query OK, 0 rows affected (0.01 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc user;
+----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+----------------+
| id | int | NO | PRI | NULL | auto_increment |
| username | varchar(45) | NO | UNI | NULL | |
| password | varchar(45) | NO | | NULL | |
| zsxm | varchar(45) | YES | | NULL | |
+----------+-------------+------+-----+---------+----------------+
4 rows in set (0.00 sec)
删除列：删除zsxm列
mysql> ALTER TABLE `test`.`user`
-> DROP COLUMN `zsxm`;
Query OK, 0 rows affected (0.02 sec)
Records: 0 Duplicates: 0 Warnings: 0
mysql> desc user;
+----------+-------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+-------------+------+-----+---------+----------------+
| id | int | NO | PRI | NULL | auto_increment |
| username | varchar(45) | NO | UNI | NULL | |
| password | varchar(45) | NO | | NULL | |
+----------+-------------+------+-----+---------+----------------+
3 rows in set (0.01 sec)
3.记录的操作
主服务器：新增，删除，修改操作比较多，
从服务器：查询操作较多
新增：
insret into 表名 （字段列表名）values (字段值列表）
mysql> select * from user;
Empty set (0.00 sec)
mysql> insert into user (id,username,password) values(3,'zhangsan','zhangsan');
Query OK, 1 row affected (0.01 sec)
mysql> select * from user;
+----+----------+----------+
| id | username | password |
+----+----------+----------+
| 3 | zhangsan | zhangsan |
+----+----------+----------+
1 row in set (0.00 sec)
如果不写字段列表名，values必须写所有的字段值并且字段类型要正确
mysql> insert into user values(3,'wangwu','wangwu');
Query OK, 1 row affected (0.00 sec)
删除：
delete from 表名 where 条件;
不加条件的时候，整个表里面的数据都会被删除
mysql> delete from user where username='zhangsan';
Query OK, 1 row affected (0.00 sec)
mysql> select * from user;
+----+----------+----------+
| id | username | password |
+----+----------+----------+
| 4 | lisi | lisi |
+----+----------+----------+
1 row in set (0.00 sec)
修改:
mysql> select * from user;
+----+----------+----------+
| id | username | password |
+----+----------+----------+
| 1 | zhangsan | zhangsan |
| 2 | lisi | lisi |
| 3 | wangwu | wangwu |
+----+----------+----------+
3 rows in set (0.00 sec)
mysql> update user set password=123 where username='zhangsan';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1 Changed: 1 Warnings: 0
mysql> select * from user;
+----+----------+----------+
| id | username | password |
+----+----------+----------+
| 1 | zhangsan | 123 |
| 2 | lisi | lisi |
| 3 | wangwu | wangwu |
+----+----------+----------+
3 rows in set (0.00 sec)