【分享】查每个分组前N条记录收藏（转）

from:http://blog.csdn.net/liangCK/archive/2008/11/13/3292540.aspx

自己又对这个有了深的了解，分享下

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2

3-- Author: liangCK 小梁

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5-- Title : 查每个分组前N条记录

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7-- Date : 2008-11-13 17:19:23

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9---------------------------------

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11

12

13--> 生成测试数据: #T

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15IF OBJECT_ID('tempdb.dbo.#T') IS NOT NULL DROP TABLE #T

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17CREATE TABLE #T (ID VARCHAR(3),GID INT,Author VARCHAR(29),Title VARCHAR(39),Date DATETIME)

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19INSERT INTO #T

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21SELECT '001',1,'邹建','深入浅出SQLServer2005开发管理与应用实例','2008-05-10' UNION ALL

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23SELECT '002',1,'胡百敬','SQLServer2005性能调校','2008-03-22' UNION ALL

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25SELECT '003',1,'格罗夫Groff.J.R.','SQL完全手册','2009-07-01' UNION ALL

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27SELECT '004',1,'KalenDelaney','SQLServer2005技术内幕存储引擎','2008-08-01' UNION ALL

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29SELECT '005',2,'Alex.Kriegel.Boris.M.Trukhnov','SQL宝典','2007-10-05' UNION ALL

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31SELECT '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

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33SELECT '007',2,'胡百敬','SQLServer2005数据库开发详解','2008-06-15' UNION ALL

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35SELECT '008',3,'陈浩奎','SQLServer2000存储过程与XML编程','2005-09-01' UNION ALL

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37SELECT '009',3,'赵松涛','SQLServer2005系统管理实录','2008-10-01' UNION ALL

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39SELECT '010',3,'黄占涛','SQL技术手册','2006-01-01'

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41

42

43--SQL查询如下:

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45

46

47--按GID分组,查每个分组中Date最新的前2条记录

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49

50

51--1.字段ID唯一时:

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53SELECT * FROM #T AS T WHERE ID IN(SELECT TOP 2 ID FROM #T WHERE GID=T.GID ORDER BY Date DESC)

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55

56

57--2.如果ID不唯一时:

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59SELECT * FROM #T AS T WHERE 2>(SELECT COUNT(*) FROM #T WHERE GID=T.GID AND Date>T.Date)

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61

62

63--SQL Server 2005 使用新方法

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65

66

67--3.使用ROW_NUMBER()进行排位分组

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69SELECT ID,GID,Author,Title,Date

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71FROM

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73(

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75 SELECT rid=ROW_NUMBER() OVER(PARTITION BY GID ORDER BY Date DESC),*

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77 FROM #T

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79) AS T

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81WHERE rid<=2

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83

84

85--4.使用APPLY

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87SELECT DISTINCT b.*

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89FROM #T AS a

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91CROSS APPLY

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93(

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95 SELECT TOP(2) * FROM #T WHERE a.GID=GID ORDER BY Date DESC

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97) AS b

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99

100

101

102

103--结果

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105

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