文章目录

• 一、用户
• • 1.用户信息
  • 2.创建用户
  • 3.删除用户
  • 4.修改用户密码
• 二、数据库的权限
• • 1.给用户授权
  • 2.回收权限

一、用户

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。

1.用户信息

我们安装mysql之后，会自动创建一个mysql的数据库。MySQL中的用户，都存储在系统数据库mysql的user表中

我们可以查询如下信息：

select host,user,authentication_string from user;  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

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 'hdp'@'localhost' identified by '123456'; Query OK, 0 rows affected (0.00 sec)  mysql> select user,host,authentication_string from user; +---------------+-----------+-------------------------------------------+ | user          | host      | authentication_string                     | +---------------+-----------+-------------------------------------------+ | root          | localhost | *5ADB87D1C6448A109DCC4D61C8C6DD5637B0683B | | mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | hdp           | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 | +---------------+-----------+-------------------------------------------+ 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'; SHOW VARIABLES LIKE 'validate_password%'; 

登录主机设置为%的时候表示可以在任意主机登录

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

3.删除用户

语法：

drop user '用户名'@'主机名' 

mysql> select user,host,authentication_string from user; +---------------+-----------+-------------------------------------------+ | user          | host      | authentication_string                     | +---------------+-----------+-------------------------------------------+ | root          | localhost | *5ADB87D1C6448A109DCC4D61C8C6DD5637B0683B | | mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | hdp           | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 | +---------------+-----------+-------------------------------------------+ 4 rows in set (0.00 sec)  mysql> drop user hdp; ERROR 1396 (HY000): Operation DROP USER failed for 'hdp'@'%' -直接给个用户名,不能删除 mysql> drop user 'hdp'@'localhost'; Query OK, 0 rows affected (0.00 sec)  mysql> select user,host,authentication_string from user; +---------------+-----------+-------------------------------------------+ | user          | host      | authentication_string                     | +---------------+-----------+-------------------------------------------+ | root          | localhost | *5ADB87D1C6448A109DCC4D61C8C6DD5637B0683B | | mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | +---------------+-----------+-------------------------------------------+ 3 rows in set (0.00 sec)  

直接给个用户名,不能进行删除，而是应该使用用户名+主机名

drop user 'hdp'@'localhost'; 

4.修改用户密码

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')； 

示例：

mysql> create user 'hdp'@'localhost' identified by '123456'; Query OK, 0 rows affected (0.00 sec)  mysql> select user,host,authentication_string from user; +---------------+-----------+-------------------------------------------+ | user          | host      | authentication_string                     | +---------------+-----------+-------------------------------------------+ | root          | localhost | *5ADB87D1C6448A109DCC4D61C8C6DD5637B0683B | | mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | hdp           | localhost | *6BB4837EB74329105EE4568DDA7DC67ED2CA2AD9 | +---------------+-----------+-------------------------------------------+ 4 rows in set (0.00 sec)  mysql> set password for 'hdp'@'localhost'=password('654321'); Query OK, 0 rows affected, 1 warning (0.00 sec)  mysql> select user,host,authentication_string from user; +---------------+-----------+-------------------------------------------+ | user          | host      | authentication_string                     | +---------------+-----------+-------------------------------------------+ | root          | localhost | *5ADB87D1C6448A109DCC4D61C8C6DD5637B0683B | | mysql.session | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | mysql.sys     | localhost | *THISISNOTAVALIDPASSWORDTHATCANBEUSEDHERE | | hdp           | localhost | *2A032F7C5BA932872F0F045E0CF6B53CF702F2C5 | +---------------+-----------+-------------------------------------------+ 4 rows in set (0.00 sec)  

二、数据库的权限

MySQL数据库提供的权限列表：

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：

1.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 

2.*.*: 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）

3.库.* : 表示某个数据库中的所有数据对象(表，视图，存储过程等)

4.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

使用root账号

mysql> show databases; +----------------------+ | Database             | +----------------------+ | information_schema   | | README_TO_RECOVER_A  | | README_TO_RECOVER_SZ | | db_test              | | mysql                | | mysql_learning       | | performance_schema   | | scott                | | sys                  | +----------------------+ 9 rows in set (0.00 sec)  mysql> use scott; 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_scott | +-----------------+ | dept            | | emp             | | salgrade        | +-----------------+ 3 rows in set (0.00 sec)  

给用户hdp赋予scott数据库下所有文件的select权限

mysql> grant select on scott.* to 'hdp'@'localhost'; Query OK, 0 rows affected (0.00 sec) 

使用hdp账号

mysql> show databases; +--------------------+ | Database           | +--------------------+ | information_schema | | scott              | +--------------------+ 2 rows in set (0.00 sec)  mysql> use scott; 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> select * from dept; +--------+------------+----------+ | deptno | dname      | loc      | +--------+------------+----------+ |     10 | ACCOUNTING | NEW YORK | |     20 | RESEARCH   | DALLAS   | |     30 | SALES      | CHICAGO  | |     40 | OPERATIONS | BOSTON   | +--------+------------+----------+ 4 rows in set (0.02 sec)  

没有删除权限

mysql> delete from dept; ERROR 1142 (42000): DELETE command denied to user 'hdp'@'localhost' for table 'dept' 

特定用户现有查看权限

how grants for 'hdp'@'localhost'; 

mysql> show grants for 'hdp'@'localhost'; +------------------------------------------------+ | Grants for hdp@localhost                       | +------------------------------------------------+ | GRANT USAGE ON *.* TO 'hdp'@'localhost'        | | GRANT SELECT ON `scott`.* TO 'hdp'@'localhost' | +------------------------------------------------+ 2 rows in set (0.00 sec)  mysql> show grants for 'root'@'localhost'; +---------------------------------------------------------------------+ | Grants for root@localhost                                           | +---------------------------------------------------------------------+ | GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION | | GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION        | +---------------------------------------------------------------------+ 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.回收权限

语法：

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

root身份回收hdp对scott数据库的所有权限

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

hdp身份

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