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---------------------------------
--? Author: liangCK 小梁
--? Title : 查每个分组前N条记录
--? Date? : 2008-11-13 17:19:23
---------------------------------
--> 生成测试数据: #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 #T
SELECT '001',1,'邹建','深入浅出SQLServer2005开发管理与应用实例','2008-05-10' UNION ALL
SELECT '002','胡百敬','SQLServer2005性能调校','2008-03-22' UNION ALL
SELECT '003','格罗夫Groff.J.R.','SQL完全手册','2009-07-01' UNION ALL
SELECT '004','KalenDelaney','SQLServer2005技术内幕存储引擎','2008-08-01' UNION ALL
SELECT '005',2,'Alex.Kriegel.Boris.M.Trukhnov','SQL宝典','2007-10-05' UNION ALL
SELECT '006','飞思科技产品研发中心','SQLServer2000高级管理与开发','2007-09-10' UNION ALL
SELECT '007','SQLServer2005数据库开发详解','2008-06-15' UNION ALL
SELECT '008',3,'陈浩奎','SQLServer2000存储过程与XML编程','2005-09-01' UNION ALL
SELECT '009','赵松涛','SQLServer2005系统管理实录','2008-10-01' UNION ALL
SELECT '010','黄占涛','SQL技术手册','2006-01-01'
--SQL查询如下:
--按GID分组,查每个分组中Date最新的前2条记录
--1.字段ID唯一时:
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不唯一时:
SELECT * FROM #T AS T WHERE 2>(SELECT COUNT(*) FROM #T WHERE GID=T.GID AND Date>T.Date)
--SQL Server 2005 使用新方法
--3.使用ROW_NUMBER()进行排位分组
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
--4.使用APPLY
SELECT DISTINCT b.*
FROM #T AS a
CROSS APPLY
(
??? SELECT TOP(2) * FROM #T WHERE a.GID=GID ORDER BY Date DESC
) AS b
--结果
/*
ID?? GID???????? Author??????????????????????? Title?????????????????????????????????? Date
---- ----------- ----------------------------- --------------------------------------- -----------------------
003? 1?????????? 格罗夫Groff.J.R.???????????????? SQL完全手册???????????????????????????????? 2009-07-01 00:00:00.000
004? 1?????????? KalenDelaney????????????????? SQLServer2005技术内幕存储引擎?????????????????? 2008-08-01 00:00:00.000
005? 2?????????? Alex.Kriegel.Boris.M.Trukhnov SQL宝典?????????????????????????????????? 2007-10-05 00:00:00.000
007? 2?????????? 胡百敬?????????????????????????? SQLServer2005数据库开发详解??????????????????? 2008-06-15 00:00:00.000
009? 3?????????? 赵松涛?????????????????????????? SQLServer2005系统管理实录???????????????????? 2008-10-01 00:00:00.000
010? 3?????????? 黄占涛?????????????????????????? SQL技术手册???????????????????????????????? 2006-01-01 00:00:00.000
(6 行受影响)
*/
?
本文来自CSDN博客，转载请标明出处：http://blog.csdn.net/htl258/archive/2009/04/12/4066478.aspx
（编辑：李大同）
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