sql查出一张表中重复的所有记录数据的三种方法,sql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)
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