13.用户管理

13. 用户管理

如果我们只能使用root用户，这样存在安全隐患。这时，就需要使用MySQL的用户管理。

13.1 用户

13.1.1 用户信息

MySQL中的用户，都存储在系统数据库mysql的user表中

mysql> use mysql;
Database changed
mysql> select host,user,authentication_string from user;
+-----------+---------------+-------------------------------------------+
| host     | user         | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| localhost | root         | *81F5E21E35407D884A6CD4A731AEBFB6AF209E1B |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
+-----------+---------------+-------------------------------------------+
--可以通过desc user初步查看一下表结构

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

13.1.2 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 'whb'@'localhost' identified by '12345678';
Query OK, 0 rows affected (0.06 sec)
mysql> select user,host,authentication_string from user;
+---------------+-----------+-------------------------------------------+
| user         | host     | authentication_string                     |
+---------------+-----------+-------------------------------------------+
| root         | %         | *A2F7C9D334175DE9AF4DB4F5473E0BD0F5FA9E75 |
| mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| whb           | localhost | *84AAC12F54AB666ECFC2A83C676908C8BBC381B1 | --新增用
户
+---------------+-----------+-------------------------------------------+
4 rows in set (0.00 sec)
-- 此时便可以使用新账号新密码进行登陆啦
--备注：可能实际在设置密码的时候，因为mysql本身的认证等级比较高，一些简单的密码无法设置，会爆出
如下报错：
-- ERROR 1819 (HY000): Your password does not satisfy the current policy 
requirements
-- 解决方案：https://blog.csdn.net/zhanaolu4821/article/details/93622812
--查看密码设置相关要求：SHOW VARIABLES LIKE 'validate_password%'; 
-- 这个大家下来自己玩玩
--关于新增用户这里，需要大家注意，不要轻易添加一个可以从任意地方登陆的user。

13.1.3 删除用户

语法：

drop user '用户名'@'主机名'

示例：

mysql> select user,host,authentication_string from user;
+---------------+-----------+-------------------------------------------+
| user         | host     | authentication_string                     |
+---------------+-----------+-------------------------------------------+
| root         | %         | *A2F7C9D334175DE9AF4DB4F5473E0BD0F5FA9E75 |
| mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| whb           | localhost | *84AAC12F54AB666ECFC2A83C676908C8BBC381B1 |
+---------------+-----------+-------------------------------------------+
4 rows in set (0.00 sec)
mysql> drop user whb;               --尝试删除
ERROR 1396 (HY000): Operation DROP USER failed for 'whb'@'%' -- <= 直接给个用户名，
不能删除，它默认是%，表示所有地方可以登陆的用户
mysql> drop user 'whb'@'localhost'; --删除用户
Query OK, 0 rows affected (0.00 sec)
mysql> select user,host,authentication_string from user;
+---------------+-----------+-------------------------------------------+
| user         | host     | authentication_string                     |
+---------------+-----------+-------------------------------------------+
| root         | %         | *A2F7C9D334175DE9AF4DB4F5473E0BD0F5FA9E75 |
| mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
+---------------+-----------+-------------------------------------------+
3 rows in set (0.00 sec)

13.1.4 修改用户密码

语法：

自己改自己密码

set password=password('新的密码');
--自己下来试试

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')；

mysql> select host,user, authentication_string from user;
+-----------+---------------+-------------------------------------------+
| host     | user         | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| %         | root         | *A2F7C9D334175DE9AF4DB4F5473E0BD0F5FA9E75 |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | whb           | *84AAC12F54AB666ECFC2A83C676908C8BBC381B1 |
+-----------+---------------+-------------------------------------------+
4 rows in set (0.00 sec)
mysql> set password for 'whb'@'localhost'=password('87654321');
Query OK, 0 rows affected, 1 warning (0.00 sec)
mysql> select host,user, authentication_string from user;
+-----------+---------------+-------------------------------------------+
| host     | user         | authentication_string                     |
+-----------+---------------+-------------------------------------------+
| %         | root         | *A2F7C9D334175DE9AF4DB4F5473E0BD0F5FA9E75 |
| localhost | mysql.session | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | mysql.sys     | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE |
| localhost | whb           | *5D24C4D94238E65A6407DFAB95AA4EA97CA2B199 |
+-----------+---------------+-------------------------------------------+
4 rows in set (0.00 sec)

13.2 数据库的权限

MySQL数据库提供的权限列表：

13.2.1 给用户授权

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

案例：

--使用root账号
--终端A
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| 57test             |
| bit_index         |
| ccdata_pro         |
| innodb_test       |
| musicserver       |
| myisam_test       |
| mysql             |
| order_sys         |
| performance_schema |
| scott             |
| sys               |
| test               |
| vod_system         |
+--------------------+
14 rows in set (0.00 sec)
mysql> use test;
Database changed
mysql> show tables;
+----------------+
| Tables_in_test |
+----------------+
| account       |
| student       |
| user           |
+----------------+
3 rows in set (0.01 sec)
--给用户whb赋予test数据库下所有文件的select权限
mysql> grant select on test.* to 'whb'@'localhost';  
Query OK, 0 rows affected (0.01 sec)
--使用whb账号
--终端B
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)
--暂停等root用户给whb赋完权之后，在查看
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| test               |  --赋完权之后，就能看到新的表
+--------------------+
2 rows in set (0.01 sec)
mysql> use test;
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> show tables;
+----------------+
| Tables_in_test |
+----------------+
| account       |
| student       |
| user           |
+----------------+
3 rows in set (0.00 sec)
mysql> select * from account;
+----+--------+---------+
| id | name   | blance |
+----+--------+---------+
|  2 | 李四   |  321.00 |
|  3 | 王五   | 5432.00 |
|  4 | 赵六   |  543.90 |
|  5 | 赵六   |  543.90 |
+----+--------+---------+
4 rows in set (0.00 sec)
--没有删除权限
mysql> delete  from account;
ERROR 1142 (42000): DELETE command denied to user 'whb'@'localhost' for table 
'account'
备注：特定用户现有查看权限
mysql> show grants for 'whb'@'%';
+-----------------------------------------------+
| Grants for whb@%                             |
+-----------------------------------------------+
| GRANT USAGE ON *.* TO 'whb'@'%'               |
| GRANT ALL PRIVILEGES ON `test`.* TO 'whb'@'%' |
+-----------------------------------------------+
2 rows in set (0.00 sec)
mysql> show grants for 'root'@'%';
+-------------------------------------------------------------+
| Grants for root@%                                           |
+-------------------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'root'@'%' WITH GRANT OPTION |
+-------------------------------------------------------------+
1 row 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;

13.2.2 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：

-- 回收whb对test数据库的所有权限
--root身份，终端A
mysql> revoke all on test.* from 'whb'@'localhost';
Query OK, 0 rows affected (0.00 sec)
--whb身份，终端B
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
| test               |
+--------------------+
2 rows in set (0.00 sec)
mysql> show databases;
+--------------------+
| Database           |
+--------------------+
| information_schema |
+--------------------+
1 row in set (0.00 sec)