SQL如何刪除重復(fù)數(shù)據(jù)

在sql中，可以使用select語(yǔ)句刪除重復(fù)數(shù)據(jù)，語(yǔ)法為：“select * from 字段 where 字段id in (select 字段id from 字段 group by 字段 having count(字段id) > 1)”。

本教程操作環(huán)境：windows7系統(tǒng)、mysql8.0版本、Dell G3電腦。

用SQL語(yǔ)句,刪除掉重復(fù)項(xiàng)只保留一條

在幾千條記錄里,存在著些相同的記錄,如何能用SQL語(yǔ)句,刪除掉重復(fù)的呢

查找表中多余的重復(fù)記錄，重復(fù)記錄是根據(jù)單個(gè)字段（peopleId）來(lái)判斷

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

擴(kuò)展：

刪除表中多余的重復(fù)記錄，重復(fù)記錄是根據(jù)單個(gè)字段（peopleId）來(lái)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)

查找表中多余的重復(fù)記錄（多個(gè)字段）

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

刪除表中多余的重復(fù)記錄（多個(gè)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)

查找表中多余的重復(fù)記錄（多個(gè)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)

消除一個(gè)字段的左邊的第一位：

update tableName set [Title]=Right([Title],(len([Title])-1)) where Title like '村%'

消除一個(gè)字段的右邊的第一位：

update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'

假刪除表中多余的重復(fù)記錄（多個(gè)字段），不包含rowid最小的記錄

update vitae set ispass=-1where peopleId in (select peopleId from vitae group by peopleId