sql 查出一张表中重复的所有记录数据

查询重复的数据
1.查询出所有数据进行分组之后，和重复数据的重复次数的查询数据，先列下：

select  count(username) as '重复次数',username from t_user group by username  having count(*)>1 order by username desc

2.查找表中多余的重复记录，重复记录是根据单个字段（peopleId）来判断

select * from people
where peopleId in (select  peopleId  from  people  group  by  peopleId  having  count(peopleId) > 1)

3.查找表中多余的重复记录（多个字段）

select * from people a
where (a.peopleId,a.seq) in  (select peopleId,seq from people group by peopleId,seq  having count(*) > 1)