a.刪除完全重復數據

create table #t1(SN varchar(30))

insert into #t1

?? values('a'),('a'),('a'),('b'),('b'),('c')

select * from (select *,ROW_NUMBER()over(partition by sn order by sn) as seq from #t1) as aa

?

delete aa from (select *,ROW_NUMBER()over(partition by sn order by sn) as seq from #t1) as aa

where aa.seq<>1

?

select * from #t1

?

b.刪除不完全重復數據

--原寫法:

注：表#tmpTrace中有多筆重復記錄，但是時間字段的值不同

DELETE a FROM #tmpTrace a

?? WHERE EXISTS(SELECT * FROM?

?? ???????(SELECT sn,station,min(TransDateTime) AS TransDateTime FROM #tmpTrace GROUP BY sn,station HAVING count(*)>1) b

?? ???????????? WHERE a.sn=b.sn AND a.TransDateTime<>b.TransDateTime and a.station=b.station)

?

--使用派生表的寫法:

delete aa from (

????????????? select *,

???????????? ROW_NUMBER()over(partition by SN,station order by TransDateTime) as Seq

????????????? from #tmpTrace

?????????? ) as aa

where aa.Seq<>1

?

--P.S:上面寫法保留的是時間最小的數據，有些時候需要保留最新的一筆數據，這樣在order by時加上DESC就可以了

轉載于:https://www.cnblogs.com/Susie2012/archive/2012/11/19/2777226.html

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