有个用户 lwx，查看user表如下：
mysql> select user,host from mysql.user;
+---------------+--------------+
| user | host |
+---------------+--------------+
| lwx | % |
| qydpw | % |
| root | % |
| root | 127.0.0.1 |
| zentao | 127.0.0.1 |
| root | ::1 |
| root | lwx |
| mysql.session | localhost |
| mysql.sys | localhost |
| qppp | localhost |
| root | localhost |
+---------------+--------------+
11 rows in set (0.00 sec)
查看下这个用户的权限，如下：
mysql> show grants for 'lwx'@'%';
+--------------------------------------------------------------------------+
| Grants for lwx@% |
+--------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'lwx'@'%' |
| GRANT SELECT ON `test`.`student` TO 'lwx'@'%' WITH GRANT OPTION |
+--------------------------------------------------------------------------+
2 rows in set (0.00 sec)
我现在想回收GRANT USAGE ON . TO 'lwx'@'%'，输入下面的语句：
mysql> revoke usage on *.* from 'lwx'@'%';
Query OK, 0 rows affected (0.00 sec)
mysql> flush privileges;
Query OK, 0 rows affected (0.00 sec)
mysql> show grants for 'lwx'@'%';
+--------------------------------------------------------------------------+
| Grants for lwx@% |
+--------------------------------------------------------------------------+
| GRANT USAGE ON *.* TO 'lwx'@'%' |
| GRANT SELECT ON `test`.`student` TO 'lwx'@'%' WITH GRANT OPTION |
+--------------------------------------------------------------------------+
2 rows in set (0.00 sec)
很明显，无法回收，为什么？
另外，权限GRANT SELECT ON test.student TO 'lwx'@'%' WITH GRANT OPTION，这个权限又如何回收呢？