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用SQL语句,删除掉重复项只保留一条

IT知识sql语句删除

从来好事天生俭，自古瓜儿苦后甜。这篇文章主要讲述用SQL语句,删除掉重复项只保留一条相关的知识，希望能为你提供帮助。


在几千条记录里,存在着些相同的记录,如何能用SQL语句,删除掉重复的呢?
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
wherepeopleName in (select peopleNamefrom people group by peopleNamehaving count(peopleName) > 1)
andpeopleId not in (select min(peopleId) from people group by peopleNamehaving count(peopleName)> 1)
【用SQL语句,删除掉重复项只保留一条】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)
6.消除一个字段的左边的第一位：
update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like 村%
7.消除一个字段的右边的第一位：
update tableName set [Title]=left([Title],(len([Title])-1)) where Title like %村
8.假删除表中多余的重复记录（多个字段），不包含rowid最小的记录
update vitae set ispass=-1
where peopleId in (select peopleId from vitae group by peopleId,seq having count(*) > 1) and seq in （select 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)





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