1.用户

1.1 用户信息

MySQL中的用户，都存储在系统数据库mysql的user表中

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

user是个表结构

字段解释：

• host： 表示这个用户可以从哪个主机登陆，如果是localhost，表示只能从本机登陆
• user： 用户名
• authentication_string： 用户密码通过password函数加密后的
• *_priv： 用户拥有的权限

1.2 创建用户

语法：
 

create user '用户名'@'登陆主机/ip' identified by '密码';

案例：

mysql> create user 'dgz'@'localhost' identified by '123456';
ERROR 1290 (HY000): The MySQL server is running with the --skip-grant-tables option so it cannot execute this statement
# 如果出现上面问题可以先刷新一下
mysql> flush privileges;
Query OK, 0 rows affected (0.01 sec)

mysql> create user 'dgz'@'localhost' identified by '123456';
Query OK, 0 rows affected (0.00 sec)

mysql> select host,user,authentication_string from user;
+-----------+---------------+-------------------------------------------+
| host      | user          | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | root          | *03CDB52F58482A55A757B2FDFA03F1A14EDA5D99 |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | dgz           | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 |
+-----------+---------------+-------------------------------------------+
4 rows in set (0.00 sec)

1.3 删除用户

语法：
 

drop user '用户名'@'主机名

案例：

mysql> drop user 'dgz'@'localhost';
Query OK, 0 rows affected (0.00 sec)

mysql> select host,user,authentication_string from user;
+-----------+---------------+-------------------------------------------+
| host      | user          | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | root          | *03CDB52F58482A55A757B2FDFA03F1A14EDA5D99 |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
+-----------+---------------+-------------------------------------------+
3 rows in set (0.00 sec)

1.4 修改用户密码

语法：
自己改自己密码

set password=password('新的密码');

root用户修改指定用户的密码

set password for '用户名'@'主机名'=password('新的密码')；

直接修改mysql库中的user表

mysql> update user set authentication_string=password('222222') where user='dgz';
Query OK, 1 row affected, 1 warning (0.00 sec)
Rows matched: 1  Changed: 1  Warnings: 1

mysql> select host,user,authentication_string from user;
+-----------+---------------+-------------------------------------------+
| host      | user          | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | root          | *03CDB52F58482A55A757B2FDFA03F1A14EDA5D99 |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | dgz           | *A0C1808B1A47CECD5C161FEE647F5427F4EB6F98 |
+-----------+---------------+-------------------------------------------+
4 rows in set (0.00 sec)

mysql> set password for 'dgz'@'localhost'=password('111111');
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> select host,user,authentication_string from user;
+-----------+---------------+-------------------------------------------+
| host      | user          | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | root          | *03CDB52F58482A55A757B2FDFA03F1A14EDA5D99 |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | dgz           | *FD571203974BA9AFE270FE62151AE967ECA5E0AA |
+-----------+---------------+-------------------------------------------+
4 rows in set (0.00 sec)

2.数据库的权限

MySQL数据库提供的权限列表：

2.1 给用户权限

刚创建的用户没有任何权限。需要给用户授权。
语法:

grant 权限列表 on 库.对象名 to '用户名'@'登陆位置' [identified by '密码']

说明：

• 权限列表，多个权限用逗号分开

  grant select on ...
  grant select, delete, create on ....
  grant all [privileges] on ... -- 表示赋予该用户在该对象上的所有权限

• *.* : 代表本系统中的所有数据库的所有对象（表，视图，存储过程等）
• 库.* : 表示某个数据库中的所有数据对象(表，视图，存储过程等)
• identified by可选。 如果用户存在，赋予权限的同时修改密码,如果该用户不存在，就是创建用户

[root@VM-8-2-centos ~]# mysql -udgz -p
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)

# dgz用户看不到其他数据库

# root端开通权限
mysql> grant all on test3.* to 'dgz'@'localhost';
Query OK, 0 rows affected (0.00 sec)

也可以只开通单个权限，如果只想让用户查看，那么可以只开通select权限

mysql> grant select test3.* to 'dgz'@'localhost';

特定用户现有查看权限

mysql> show grants for 'dgz'@'localhost';
+--------------------------------------------------------+
| Grants for dgz@localhost                               |
+--------------------------------------------------------+
| GRANT USAGE ON *.* TO 'dgz'@'localhost'                |
| GRANT ALL PRIVILEGES ON `test3`.* TO 'dgz'@'localhost' |
+--------------------------------------------------------+
2 rows in set (0.00 sec)

注意：如果发现赋权限后，没有生效，执行如下指令：

flush privileges;

2.2 回收权限

语法：

revoke 权限列表 on 库.对象名 from '用户名'@'登陆位置'；

示例：
 

mysql> revoke all on test3.* from 'dgz'@'localhost';
Query OK, 0 rows affected (0.00 sec)

mysql> show grants for 'dgz'@'localhost';
+-----------------------------------------+
| Grants for dgz@localhost                |
+-----------------------------------------+
| GRANT USAGE ON *.* TO 'dgz'@'localhost' |
+-----------------------------------------+
1 row in set (0.00 sec)

用户dgz查看不到test3库了

mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)