**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
sql
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：
sql
create user '用户名'@'登陆主机/ip' identified by '密码';案例：
sql
create user '张莹莹'@localhost identified by '123456';
远程登录
create user '张莹莹'@'%' identified by '123456'; 查看：
sql
select user,host,authentication_string from user\G;
sql
*************************** 1. row ***************************
user: 张莹莹
host: lenovo
authentication_string: $A$005$qyB␦1j>>><nRHfxUbembrPh4cPlU4K6lbgn5hCOa7VdfMO6bPXBT/1ZJ/
*************************** 2. row ***************************
user: mysql.infoschema
host: localhost
authentication_string: $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED
*************************** 3. row ***************************
user: mysql.session
host: localhost
authentication_string: $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED
*************************** 4. row ***************************
user: mysql.sys
host: localhost
authentication_string: $A$005$THISISACOMBINATIONOFINVALIDSALTANDPASSWORDTHATMUSTNEVERBRBEUSED
*************************** 5. row ***************************
user: root
host: localhost -- 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：
sql
drop user '用户名'@'主机名'
sql
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：
自己改自己的密码：
sql
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：
sql
-- 如果用户存在
ALTER USER 'zyy'@'%' IDENTIFIED BY '123456abc';
-- 如果用户不存在，先创建用户再设置密码
CREATE USER 'zyy'@'%' IDENTIFIED BY '123456abc';
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> select user();
+----------------+
| user() |
+----------------+
| root@localhost |
+----------------+
localhost: 本地环境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:
sql
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
sql
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
sql
--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 |
+--------------------+
注意：如果发现赋权限后，没有生效，执行如下指令：
| 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：
sql
revoke 权限列表 on 库.对象名 from '用户名'@'登陆位置'；示例：
sql
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)