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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¡¢NameÏàͬID×îСµÄ¼Ç¼(ÍƼöÓÃ1,2,3),±£Áô×îСһÌõ
·½·¨1:
delete a from #T a where  exists(select 1 from #T where Name=a.Name and ID<a.ID)
·½·¨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
·½·¨3:
delete a from #T a where ID not in (select min(ID) from #T where Name=a.Name)
·½·¨4(×¢:IDΪΨһʱ¿ÉÓÃ):
delete a from #T a where ID not in(select min(ID)from #T group by Name)
·½·¨5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID<a.ID)>0
·½·¨6:
delete a from #T a where ID<>(select top 1 ID from #T where Name=a.name order by ID)
·½·¨7:
delete a from #T a where ID>any(select ID from #T where Name=a.Name)
select * from #T
Éú³É½á¹û:
/*
ID          Name Memo
----------- ---- ----
1           A    A1
4           B    B1
(2 ÐÐÊÜÓ°Ïì)
*/
--II¡¢NameÏàͬID±£Áô×î´óµÄÒ»Ìõ¼Ç¼:
·½·¨1:
delete a from #T a where  exists(select 1 from #T where Name=a.Name and ID>a.ID)
·½·¨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
·½·¨3:
delete a from #T a where ID not in (select max(ID) from #T where Name=a.Name)
·½·¨4(×¢:IDΪΨһʱ¿ÉÓÃ):
delete a from #T a where ID not in(select max(ID)from #T group by Name)
·½·¨5:
delete a from #T a where (select count(1) from #T where Name=a.Name and ID>a.ID)>0
·½·¨6:
delete a from #T a where ID<>(select top 1 ID fr