use mysql;

mysql> select host,user from user;

+-----------+---------------+

| host      | user          |

+-----------+---------------+

| %         | root          |

| localhost | mysql.session |

| localhost | mysql.sys     |

| localhost | root          |

+-----------+---------------+

 rows in set (0.00 sec)

select host,user from user where user='root';

update user set host='%' where user='root';

update user set host='localhost' where user='root' and host='192.168.%.%';

//ERROR 1062 (23000): Duplicate entry '%-root' for key 'PRIMARY' 不予理会

flush privileges

grant all privileges on *.* to 'root'@'172.18.%.%' identified by '' with grant option;

grant all privileges on *.* to 'root'@'192.168.1.%' identified by '' with grant option;

revoke all privileges on *.* from root@'%';

revoke all privileges on db01.* from root@'%';

drop user 'test'@'localhost';

mysql> SHOW GRANTS FOR 'user01'@'%';

+--------------------------------------------------------+

| Grants for user01@%                                 |

+--------------------------------------------------------+

| GRANT USAGE ON *.* TO 'root'@'%'                  |

| GRANT ALL PRIVILEGES ON `db01`.* TO 'user01'@'%' |

+--------------------------------------------------------+

 rows in set (0.00 sec)

//USAGE:create user时的默认的空权限，只能连库，所以user01现在的权限是在mysql01数据库上有所有的权限。