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 程式師世界 >> 數據庫知識 >> 其他數據庫知識 >> 更多數據庫知識 >> SQL語句實現刪除重復記錄並只保留一條

SQL語句實現刪除重復記錄並只保留一條

編輯:更多數據庫知識

復制代碼 代碼如下:
delete WeiBoTopics where Id in(select max(Id) from WeiBoTopics group by WeiBoId,Title having COUNT(*) > 1);

SQL:刪除重復數據,只保留一條用SQL語句,刪除掉重復項只保留一條在幾千條記錄裡,存在著些相同的記錄,如何能用SQL語句,刪除掉重復的呢

1、查找表中多余的重復記錄,重復記錄是根據單個字段(peopleId)來判斷
復制代碼 代碼如下:
 select * from people where peopleId in (select peopleId from people group by peopleId having count(peopleId) > 1)

2、刪除表中多余的重復記錄,重復記錄是根據單個字段(peopleId)來判斷,只留有rowid最小的記錄
復制代碼 代碼如下:
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、查找表中多余的重復記錄(多個字段)
復制代碼 代碼如下:
select * from vitae a where (a.peopleId,a.seq) in (select peopleId,seq from vitae group by peopleId,seq having count(*) > 1)

4、刪除表中多余的重復記錄(多個字段),只留有rowid最小的記錄
復制代碼 代碼如下:
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、查找表中多余的重復記錄(多個字段),不包含rowid最小的記錄
復制代碼 代碼如下:
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:
復制代碼 代碼如下:
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:
復制代碼 代碼如下:
update tableName set [Title]=left([Title],(len([Title])-1)) where Title like '%村'

8.假刪除表中多余的重復記錄(多個字段),不包含rowid最小的記錄
復制代碼 代碼如下:
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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