下文为您介绍的是使用SQL语句查询每个分组的前N条记录的实现方法,如果您在此方面曾经遇到过问题,不妨一看,对您学习SQL语句使用有所帮助。
- --> 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',1,'胡百敬','SQLServer2005性能调校','2008-03-22' UNION ALL
- SELECT '003',1,'格罗夫Groff.J.R.','SQL完全手册','2009-07-01' UNION ALL
- SELECT '004',1,'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',2,'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',2,'胡百敬','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',3,'赵松涛','SQLServer2005系统管理实录','2008-10-01' UNION ALL
- SELECT '010',3,'黄占涛','SQL技术手册','2006-01-01'UNION ALL
- SELECT '010',4,'黄蛋蛋','SQL技术手册蛋蛋','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
-
- select * from #T
-
- --1.字段ID唯一时:
- SELECT * FROM #T AS T WHERE ID IN(SELECT TOP 3 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
-
-
- select * from #T