MySQL学习笔记16

MySQL的用户管理和权限管理：

在MySQL中创建更多的用户，不可能都使用root用户。root用户的权限太高，一个误操作，容易造成很大的失误。

注意：MySQL中不能单纯通过用户名来说明用户，必须加上主机，如jack@10.1.1.1

1、语法：

创建用户的时候，直接设置密码。

mysql> create user '用户名'@'被允许连接的主机名称或主机的IP地址' identified by '用户密码';
mysql> select user,host from mysql.user;

2、创建MySQL账号，用户名tom，用户密码：123

mysql> create user 'tom'@'localhost' identified by '123';
Query OK, 0 rows affected (0.00 sec)
 
mysql> select user,host from mysql.user;
+---------------+-----------+
| user          | host      |
+---------------+-----------+
| mysql.session | localhost |
| mysql.sys     | localhost |
| root          | localhost |
| tom           | localhost |
+---------------+-----------+
4 rows in set (0.00 sec)

该tom用户只能本地访问。localhost本机访问。

我们通过navicat软件进行登录，发现登录不上，这是因为root账号只能本地登录。

案例：创建一个mysql账号，要求开通远程连接。主机ip地址192.168.17.125，用户名harry，密码：123。

create user 'harry'@'192.168.17.125' identified by '123';

然后在192.168.17.125服务器上进行测试：

[root@mysql-test ~]# mysql -h 192.168.17.123 -uharry -p
Enter password:
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 3
Server version: 5.7.43 MySQL Community Server (GPL)
 
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
 
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
 
MySQL [(none)]>
MySQL [(none)]>
MySQL [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)
 

说明：

yum install mysql -y

yum安装mysql：代表安装的是mysql客户端；

yum安装mysql-server：代表安装的mysql-server服务器端；

案例：创建一个MySQL账号（要求开通远程连接），主机IP的网段：10.1.1.0，用户名：jack，用户密码：123

mysql> create user 'jack'@'192.168.17.%' identified by '123';
Query OK, 0 rows affected (0.04 sec)
 
mysql>
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| 192.168.17.%   | jack          |
| 192.168.17.125 | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
| localhost      | tom           |
+----------------+---------------+
6 rows in set (0.00 sec)
 
 
 
[root@mysql-test ~]# mysql -h 192.168.17.123 -ujack -p
Enter password:
Welcome to the MariaDB monitor.  Commands end with ; or \g.
Your MySQL connection id is 4
Server version: 5.7.43 MySQL Community Server (GPL)
 
Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others.
 
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
 
MySQL [(none)]>
MySQL [(none)]>
MySQL [(none)]> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)

案例：创建一个MySQL账号（要求开通远程连接），要求面向所有主机开放，用户名：root，用户密码：123。

mysql> create user 'root'@'%' identified by '123';
Query OK, 0 rows affected (0.00 sec)
 
mysql>
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| %              | root          |
| 192.168.17.%   | jack          |
| 192.168.17.125 | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
| localhost      | tom           |
+----------------+---------------+
7 rows in set (0.00 sec)
 

MySQL里面的账号不能仅仅看账号，也要看IP地址。由这两个决定一个账号。

删除账号：

基本语法：

mysql> drop user '用户名'@'主机名称或主机的IP地址';
特别说明：
如果在删除用户时没有指定主机的名称或主机的IP地址，则默认删除这个账号的所有信息。

案例：删除tom这个账号。

mysql> drop user 'tom'@'localhost';
Query OK, 0 rows affected (0.00 sec)
 
mysql>
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| %              | root          |
| 192.168.17.%   | jack          |
| 192.168.17.125 | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
+----------------+---------------+
6 rows in set (0.00 sec)

案例：删除jack这个账号。

mysql> drop user 'jack'@'192.168.17.%';
Query OK, 0 rows affected (0.00 sec)
 
mysql>
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| %              | root          |
| 192.168.17.125 | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
+----------------+---------------+
5 rows in set (0.00 sec)

扩展：删除MySQL账号的另外一种方式。

mysql> delete from mysql.user where user='root' and host='%';
Query OK, 1 row affected (0.00 sec)
 
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| 192.168.17.125 | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
+----------------+---------------+
4 rows in set (0.00 sec)

修改MySQL账号：

特别说明：MySQL用户重命名通常可以更改两部分，一部分是用户的名称，一部分是被允许访问的主机名称或主机的IP地址。

基本语法：

mysql> rename user 旧用户信息 to 新用户信息;

案例：把用户'root'@'%'更改为'root'@'10.1.1.%'。

mysql> create user 'root'@'%' identified by '123';
Query OK, 0 rows affected (0.00 sec)
 
mysql>
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| %              | root          |
| 192.168.17.125 | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
+----------------+---------------+
5 rows in set (0.00 sec)
 
 
mysql> rename user 'root'@'%' to 'root'@'192.168.17.%';
Query OK, 0 rows affected (0.00 sec)
 
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| 192.168.17.%   | root          |
| 192.168.17.125 | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
+----------------+---------------+
5 rows in set (0.00 sec)
 

mysql> create user 'tom'@'localhost' identified by '123';
Query OK, 0 rows affected (0.00 sec)
 
mysql> rename user 'tom'@'localhost' to 'harry'@'localhost';
Query OK, 0 rows affected (0.00 sec)
 
mysql>
mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| 192.168.17.%   | root          |
| 192.168.17.125 | harry         |
| localhost      | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
+----------------+---------------+
6 rows in set (0.00 sec)

扩展：使用update语句更新用户信息

mysql> select host, user from mysql.user;
+----------------+---------------+
| host           | user          |
+----------------+---------------+
| 192.168.17.%   | root          |
| 192.168.17.125 | harry         |
| localhost      | harry         |
| localhost      | mysql.session |
| localhost      | mysql.sys     |
| localhost      | root          |
+----------------+---------------+
6 rows in set (0.00 sec)
 
 
 
mysql> update mysql.user set user='tom', host='localhost' where user='harry' and host='localhost';
Query OK, 1 row affected (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 0
 
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)