MYSQL 删除表内重复记录

MYSQL 数据库

表内UserName字段存在很多重复记录

求一个删除的语句，要求重复记录保留一条ID最小的。

delete from radcheck where username in (select * from ( select username from radcheck group by username having count( * )>1) b where radcheck.username=b.username) and id not in (select * from ( select min(id) as id from radcheck group by username) c where radcheck.id=c.id)

这样就可以了