浅析drop user与delete from mysql.user的区别

drop  user 会将该用户的信息全部删掉，而 delete  只会清除user表，其他的比如db表中的信息还是存在。
如果delete 后，再创建一个最小权限的用户，那么他会重用以前的权限。
grant all on test.* to 'test'@'%' identified by 'test';
delete  from user  where  user =test;
差看db 表
mysql> select * from db;
+------+---------+------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
| host | db      | user | select_priv | insert_priv | update_priv | delete_priv | create_priv | drop_priv | grant_priv | references_priv | index_priv | alter_priv | create_tmp_table_priv | lock_tables_priv | create_view_priv | show_view_priv | create_routine_priv | alter_routine_priv | execute_priv | event_priv | trigger_priv |
+------+---------+------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
| %    | test    |      | y           | y           | y           | y           | y           | y         | n          | y               | y          | y          | y                     | y                | y                | y              | y                   | n                  | n            | y          | y            |
| %    | test\_% |      | y           | y           | y           | y           | y           | y         | n          | y               | y          | y          | y                     | y                | y                | y              | y                   | n                  | n            | y          | y            |
| %    | test    | test | y           | y           | y           | y           | y           | y         | n          | y               | y          | y          | y                     | y                | y                | y              | y                   | y                  | y            | y          | y            |
+------+---------+------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
3 rows in set (0.00 sec)
test  的权限依然存在
创建一个只有select 的 用户test
grant select  on test.* to 'test'@'%' identified by 'test';
mysql> select * from db;
+------+---------+------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
| host | db      | user | select_priv | insert_priv | update_priv | delete_priv | create_priv | drop_priv | grant_priv | references_priv | index_priv | alter_priv | create_tmp_table_priv | lock_tables_priv | create_view_priv | show_view_priv | create_routine_priv | alter_routine_priv | execute_priv | event_priv | trigger_priv |
+------+---------+------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
| %    | test    |      | y           | y           | y           | y           | y           | y         | n          | y               | y          | y          | y                     | y                | y                | y              | y                   | n                  | n            | y          | y            |
| %    | test\_% |      | y           | y           | y           | y           | y           | y         | n          | y               | y          | y          | y                     | y                | y                | y              | y                   | n                  | n            | y          | y            |
| %    | test    | test | y           | y           | y           | y           | y           | y         | n          | y               | y          | y          | y                     | y                | y                | y              | y                   | y                  | y            | y          | y            |
+------+---------+------+-------------+-------------+-------------+-------------+-------------+-----------+------------+-----------------+------------+------------+-----------------------+------------------+------------------+----------------+---------------------+--------------------+--------------+------------+--------------+
3 rows in set (0.00 sec)
权限和以前的一样。