SQL查詢每個分組的前N條記錄

if object_id('tempdb.dbo.#t') is not null drop table #t

create table #t (id varchar(3),gid int,author varchar(29),title varchar(39),date datetime)

insert into #t

select '001',1,'鄒建','深入淺出sqlserver2005開發管理與應用例項','2008-05-10' union all

select '002',1,'胡百敬','sqlserver2005效能調校','2008-03-22' union all

select '003',1,'格羅夫groff.j.r.','sql完全手刪','2009-07-01' union all

select '004',1,'kalendelaney','sqlserver2005技術內幕儲存引擎','2008-08-01' union all

select '005',2,'alex.kriegel.boris.m.trukhnov','sql寶典','2007-10-05' union all

select '006',2,'飛思科技產品研發中心','sqlserver2000高階管理與開發','2007-09-10' union all

select '007',2,'胡百敬','sqlserver2005資料庫開發詳解','2008-06-15' union all

select '008',3,'陳浩奎','sqlserver2000儲存過程與xml程式設計','2005-09-01' union all

select '009',3,'趙松濤','sqlserver2005系統管理實錄','2008-10-01' union all

select '010',3,'黃佔濤','sql技術手冊','2006-01-01'

--sql查詢如下:

--按gid分組,查每個分組date最新的前2條記錄

--1.欄位id唯一時:

select * from #t as t where id in(select top 2 id from #t where gid=t.gid order by date desc)

--2.如果id不唯一時:

select * from #t as t where 2>(select count(*) from #t where gid=t.gid and date>t.date)

--sqlserver 2005 使用新方法

--3.使用row_number()進行排位分組

select id,gid,author,title,date

from

( select rid=row_number()

over(partition by gid

order by date desc),

* from #t

) as t

where rid<=2

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