用SQL語句,刪除掉重複項只保留一條
在幾千條記錄裏,存在着些相同的記錄,如何能用SQL語句,刪除掉重複的呢
1、查找表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷
select * from people
where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)
2、刪除表中多餘的重複記錄，重複記錄是根據單個字段（peopleId）來判斷，只留有rowid最小的記錄
delete from people
where peopleName in (select peopleName from people group by peopleName having count(peopleName) > 1)
and peopleId not in (select min(peopleId) from people group by peopleName having count(peopleName)>1)
3、查找表中多餘的重複記錄（多個字段）
select * from vitae a
where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)
4、刪除表中多餘的重複記錄（多個字段），只留有rowid最小的記錄
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、查找表中多餘的重複記錄（多個字段），不包含rowid最小的記錄
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.消除一個字段的左邊的第一位：
update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like '村%'
7.消除一個字段的右邊的第一位：
update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'
8.假刪除表中多餘的重複記錄（多個字段），不包含rowid最小的記錄
update vitae set ispass=-1
where peopleId in (select peopleId from vitae group by peopleId
來自：http://blog.csdn.net/anya/article/details/6407280/