sql语句中查重复数据

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查找所有重复标题的记录:

SELECT *

FROM t_info a

WHERE ((SELECT COUNT(*)

FROM t_info

WHERE Title = a.Title) > 1)

ORDER BY Title DESC

⼀。查找重复记录

1。查找全部重复记录

Select * From 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。过滤重复记录(只显⽰⼀条)

Select * From HZT Where ID In (Select Max(ID) From HZT Group By Title

注:此处显⽰ID最⼤⼀条记录

⼆。删除重复记录

1。删除全部重复记录(慎⽤)

Delete 表 Where 重复字段 In (Select 重复字段 From 表 Group By 重复字段 Having Count(*)>1)

2。保留⼀条(这个应该是⼤多数⼈所需要的 ^_^)

Delete HZT Where ID Not In (Select Max(ID) From HZT Group By Title)

注:此处保留ID最⼤⼀条记录

1、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)

2、删除表中多余的重复记录,重复记录是根据单个字段(peopleId)来判断,只留有rowid最⼩的记录

delete from people

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

and rowid not in (select min(rowid) 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 vitae a

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

4、删除表中多余的重复记录(多个字段),只留有rowid最⼩的记录

delete from vitae a

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

and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

5、查找表中多余的重复记录(多个字段),不包含rowid最⼩的记录

select * from vitae a

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

and rowid not in (select min(rowid) from vitae group by peopleId,seq having count(*)>1)

补充:

有两个以上的重复记录,⼀是完全重复的记录,也即所有字段均重复的记录,⼆是部分关键字段重复的记录,⽐如Name字段重复,⽽其他

字段不⼀定重复或都重复可以忽略。

1、对于第⼀种重复,⽐较容易解决,使⽤

select distinct * from tableName

就可以得到⽆重复记录的结果集。

如果该表需要删除重复的记录(重复记录保留1条),可以按以下⽅法删除

select distinct * into #Tmp from tableName

drop table tableName

select * into tableName from #Tmp

drop table #Tmp

发⽣这种重复的原因是表设计不周产⽣的,增加唯⼀索引列即可解决。

2、这类重复问题通常要求保留重复记录中的第⼀条记录,操作⽅法如下

假设有重复的字段为Name,Address,要求得到这两个字段唯⼀的结果集

select identity(int,1,1) as autoID, * into #Tmp from tableName

select min(autoID) as autoID into #Tmp2 from #Tmp group by Name,autoID

select * from #Tmp where autoID in(select autoID from #tmp2)