搜索关键字：

• mysql 删除用户 delete drop
• linux mysql delete user
• mysql delete vs drop user

参考链接：

• http://stackoverflow.com/questions/10560268/difference-between-drop-user-and-deleting-a-row-from-the-mysql-user-table
• http://stackoverflow.com/questions/8555154/what-is-the-difference-between-drop-and-delete-for-tables
• http://saadiya.blog.51cto.com/2805761/1109847
• http://www.liquidweb.com/kb/remove-a-mysql-user-on-linux-via-command-line/
• http://www.liquidweb.com/kb/remove-permissions-for-a-mysql-user-on-linux-via-command-line/
• =
• http://blog.sae.sina.com.cn/archives/1912
• http://wolfchen.blog.51cto.com/2211749/1243990
• https://dev.mysql.com/doc/refman/5.5/en/privileges-provided.html
• https://dev.mysql.com/doc/refman/5.5/en/grant.html
• http://dev.mysql.com/doc/refman/5.5/en/drop-table.html
• http://dev.mysql.com/doc/refman/5.5/en/delete.html

参考解答：

（方法一）drop user 用户名;

作用：删除已经存在的用户，例如要删除 abc 这个用户，(drop user abc;)默认删除的是 abc@”%” 这个用户，如果还有其他用户，例如 abc@”localhost”, abc@”ip” ，则不会一起被删除。如果只存在一个用户 abc@”localhost” ，使用语句(drop user abc;)会报错，应该用(drop user abc@”localhost”;)如果不能确定（用户名@机器名）中的机器名，可以在mysql中的user表中进行查找，user列对应的是用户名，host列对应的是机器名。[删除账户及权限]

（方法二）delete from user where user=”用户名” and host=”机器名”;

delete也是删除用户的方法，例如要删除 abc@”localhost” 用户，则可以(delete from mysql.user where user=”abc” and host=”localhost”;)[删除账户]

注：drop删除掉的用户不仅将user表中的数据删除，还会删除诸如db和其他权限表的内容。而（方法二）只是删除了user表的内容，其他表不会被删除，后期如果命名一个和已删除用户相同的名字，权限就会被继承。

root@localhost [(none)]> status;
--------------
mysql  Ver 14.14 Distrib 5.6.25-73.1, for Linux (x86_64) using  6.3
...
Server version:        5.6.25-73.1 MySQL Community Server (GPL)


> select host,user,password from mysql.user;
> select host,user,password from mysql.user where user='';

> show grants for ''@localhost;
> drop user ''@localhost;
> flush privileges;

> select host,user,password from mysql.user;

> use mysql;
> update user set password=password('new-password-here') where user='root';

> select host,user,password from mysql.user;

• https://dev.mysql.com/doc/refman/5.5/en/removing-users.html
• https://dev.mysql.com/doc/refman/5.5/en/drop-user.html

==
DROP is used to remove tables (and databases).
DELETE is used to delete rows from tables.
==

/* 删除表中的[所有]记录 */
delete from mydb.mytable;

TRUNCATE TABLE mydb.mytable;

/* 在删除所有记录后重置 autoincrement 的值 */
ALTER TABLE `mytable` AUTO_INCREMENT = 1;

SELECT MIN(`column`) FROM `mytable`;
SELECT MAX(`column`) FROM `mytable`;

=EOF=