sql查出一张表中重复的所有记录数据的三种方法

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 xi 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)