关于MySql删除表中重复数据

今天在删除MySQL表中重复数据的时候，遇到一些问题，在这里做一些笔记。

创建一个表测试create table user(
id int not null primary key auto_increment,
name varchar(20),
password varchar(20)
)为表添加数据



接下来查询重复数据

select username from n_user group by username having count(username)>1
结果



删除重复数据

delete from user where name in(
select name from user group by name having count(name)>1
)结果



查了一下，MySQL在查询后又执行删除操作就会报这个错，解决办法是在查询语句外面再嵌套一层查询，如下

delete from user where name in(
select name from(
select name from user group by name having count(name)>1
) as aa
)这里还有一个套就是如果没给查询设置别名，报这个错



错误解决，再次执行，就可以成功删除表中重复数据了

要保留重复数据中的一条记录，这样写

delete from user where name in(
select name from(
select name from user group by name having count(name)>1
) as aa
) and id not in(
select id from(
select min(id) id from user group by name having count(name)>1
) as ab
)