SQL語句查詢每個(gè)分組的前N條記錄的實(shí)現(xiàn)方法：

1、生成測試數(shù)據(jù): #T

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 #Tselect "001", 1, "鄒建", "深入淺出SQLServer2005開發(fā)管理與應(yīng)用實(shí)例", "2008-05-10"union allselect "002", 1, "胡百敬", "SQLServer2005性能調(diào)校", "2008-03-22"union allselect "003", 1, "格羅夫Groff.J.R.", "SQL完全手冊", "2009-07-01"union allselect "004", 1, "KalenDelaney", "SQLServer2005技術(shù)內(nèi)幕存儲(chǔ)引擎", "2008-08-01"union allselect "005", 2, "Alex.Kriegel.Boris.M.Trukhnov", "SQL寶典", "2007-10-05"union allselect "006", 2, "飛思科技產(chǎn)品研發(fā)中心", "SQLServer2000高級(jí)管理與開發(fā)", "2007-09-10"union allselect "007", 2, "胡百敬", "SQLServer2005數(shù)據(jù)庫開發(fā)詳解", "2008-06-15"union allselect "008", 3, "陳浩奎", "SQLServer2000存儲(chǔ)過程與XML編程", "2005-09-01"union allselect "009", 3, "趙松濤", "SQLServer2005系統(tǒng)管理實(shí)錄", "2008-10-01"union allselect "010", 3, "黃占濤", "SQL技術(shù)手冊", "2006-01-01"union allselect "010", 4, "黃蛋蛋", "SQL技術(shù)手冊蛋蛋", "2006-01-01";

2、表記錄查詢?nèi)缦?

select * from #T;

結(jié)果：

3、按GID分組,查每個(gè)分組中Date最新的前2條記錄

（1）用子查詢

--1.字段ID唯一時(shí): select *from #T as Twhere ID in (select top 2 ID from #T where GID=T.GID order by Date desc);--2.如果ID不唯一時(shí): select *from #T as Twhere 2>(select count(*)from #T where GID=T.GID and Date>T.Date);

（2）使用SQL Server 2005 使用新方法ROW_NUMBER()進(jìn)行排位分組

select ID, GID, Author, Title, Datefrom(       select rid=row_number() over (partition by GID order by Date desc), * from #T) as Twhere rid<=2;

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