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MSSQL处理表重复记录

 2012-10-29 13:44:13 来源:WEB开发网   
核心提示:方法9(注:ID为唯一时可用):select * from #T a where ID in(select max(ID) from #T group by Name)--SQL2005:方法10:select ID,Name,Memo from (select *,max(ID)over(partition by N


方法9(注:ID为唯一时可用):
select * from #T a where ID in(select max(ID) from #T group by Name)


--SQL2005:


方法10:
select ID,Name,Memo from (select *,max(ID)over(partition by Name) as MinID from #T a)T where ID=MinID


方法11:
select ID,Name,Memo from (select *,row_number()over(partition by Name order by ID desc) as MinID from #T a)T where MinID=1


生成结果2:
/*
ID Name Memo
----------- ---- ----
3 A A3
5 B B2


(2 行受影响)
*/


--2、删除重复记录有大小关系时,保留大或小其中一个记录 本文来自:http://www.52mvc.com/originalstory/list.aspx


--> --> (Roy)生成測試數據


if not object_id('Tempdb..#T') is null
drop table #T
Go
Create table #T([ID] int,[Name] nvarchar(1),[Memo] nvarchar(2))
Insert #T
select 1,N'A',N'A1' union all
select 2,N'A',N'A2' union all
select 3,N'A',N'A3' union all
select 4,N'B',N'B1' union all
select 5,N'B',N'B2'
Go


--I、Name相同ID最小的记录(推荐用1,2,3),保留最小一条
方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID<a.ID)


方法2:
delete a from #T a left join (select min(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null


方法3:
delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)


方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select min(ID)from #T group by Name)


方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0


方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)


方法7:
delete a from #T a where ID>any(select ID from #T where Name=a.Name)


select * from #T


生成结果:
/*
ID Name Memo
----------- ---- ----
1 A A1
4 B B1


(2 行受影响)
*/


--II、Name相同ID保留最大的一条记录:


方法1:
delete a from #T a where exists(select 1 from #T where Name=a.Name and ID>a.ID)


方法2:
delete a from #T a left join (select max(ID)ID,Name from #T group by Name) b on a.Name=b.Name and a.ID=b.ID where b.Id is null


方法3:
delete a from #T a where ID not in (select max(ID) from #T where Name=a.Name)


方法4(注:ID为唯一时可用):
delete a from #T a where ID not in(select max(ID)from #T group by Name)


方法5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)>0


方法6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID desc)


方法7:
delete a from #T a where ID<any(select ID from #T where Name=a.Name)


select * from #T
/*
ID Name Memo
----------- ---- ----
3 A A3

Tags:MSSQL 处理 重复

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