如筛选出来一个字段中的重复记录
如表a
id username password
1 1 1
2 1 1
3 2 2
4 2[ 4
如何将username中有重复的记录全部筛选出来，新手求指导。
------解决方案--------------------------------------------------------
- SQL code
select * from 表a where username in ( select username from 表a group by username having count(*) > 1)
------解决方案--------------------------------------------------------
select * from 如表a t where exists (select 1 from 如表a where username=t.username and id!=t.id)