mysql中删除用户权限
revoke:只删除了用户权限，但没有删除这个用户
mysql> select user,host from user;
+------------------+-----------+
| user | host |
+------------------+-----------+
| root | 127.0.0.1 |
| debian-sys-maint | localhost |
| root | localhost |
| xbb | localhost |
| root | wangxg |
+------------------+-----------+
mysql> revoke insert,update,delete,select ON *.* from 'xbb'@'localhost' IDENTIFIED BY '123';
mysql> select user,host from user;
+------------------+-----------+
| user | host |
+------------------+-----------+
| root | 127.0.0.1 |
| debian-sys-maint | localhost |
| root | localhost |
| xbb | localhost |
| root | wangxg |
+------------------+-----------+
5 rows in set (0.00 sec)
mysql> show grants for xbb@localhost;
+------------------------------------------------------------------------------------------------------------+
| Grants for xbb@localhost |
+------------------------------------------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'xbb'@'localhost' IDENTIFIED BY PASSWORD '*23AE809DDACAF96AF0FD78ED04B6A265E05AA257' |
+------------------------------------------------------------------------------------------------------------+
drop user:删除了整个用户及其权限（包括数据字典中的数据）
mysql> drop user 'xbb'@'localhost';
Query OK, 0 rows affected (0.00 sec)
mysql> select user,host from user;
+------------------+-----------+
| user | host |
+------------------+-----------+
| root | 127.0.0.1 |
| debian-sys-maint | localhost |
| root | localhost |
| root | wangxg |
+------------------+-----------+
4 rows in set (0.00 sec)
delete from user:删除了mysql库中某一用户，（但不能删除数据字典【information_schema】中相关的记录）
mysql> GRANT insert,update,delete,select ON *.* TO 'xbb'@'localhost' IDENTIFIED BY '123';
Query OK, 0 rows affected (0.00 sec)
mysql> select user,host from user;
+------------------+-----------+
| user | host |
+------------------+-----------+
| root | 127.0.0.1 |
| debian-sys-maint | localhost |
| root | localhost |
| xbb | localhost |
| root | wangxg |
+------------------+-----------+
5 rows in set (0.00 sec)
mysql> delect * from user where user ='xbb';
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'delect * from user where user ='xbb'' at line 1
mysql> delete * from user where user ='xbb';
ERROR 1064 (42000): You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '* from user where user ='xbb'' at line 1
mysql> delete from user where user ='xbb';
Query OK, 1 row affected (0.09 sec)
mysql> select user,host from user;
+------------------+-----------+
| user | host |
+------------------+-----------+
| root | 127.0.0.1 |
| debian-sys-maint | localhost |
| root | localhost |
| root | wangxg |
+------------------+-----------+
4 rows in set (0.00 sec)