SQL如何刪除重複數據

在sql中，可以使用select語句刪除重複數據，語法為：“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)” 。

本教學操作環境：windows7系統、mysql8.0版本、Dell G3電腦。

用SQL語句,刪除掉重複項只保留一條

在幾千筆記錄裡,存在著些相同的記錄,如何能用SQL語句,刪除掉重複的呢

查找表中多餘的重複記錄，重複記錄是根據單一欄位（peopleId）來判斷 

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

#擴充：

刪除表中多餘的重複記錄，重複記錄是根據單一欄位（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)

查找表中多餘的重複記錄（多個欄位）

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

 刪除表中多餘的重複記錄（多個欄位），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)

查找表中多餘的重複記錄（多個欄位），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)

消除一個欄位的左邊的第一位：

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

消除一個欄位的右邊的第一位：

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

假刪除表中多餘的重複記錄（多個欄位），不包含rowid最小的記錄

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

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