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  • 分组查找前几条数据

    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'

    --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
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  • 原文地址:https://www.cnblogs.com/happyday56/p/1564769.html
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