SQL Server 2008 R2——ROW_NUMBER() 去掉不同行中相同列的重复内容

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总是写一些“战5渣”的东西，这次来个“战6渣”的。不然没法混了。

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 举个例子，不一定好。

原创例子，必然没有雷同。

这个栗子果然坏了。

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将弄成这个样子。

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 1 USE tempdb

 2 GO

 3 --------------------------------------------------------------------------

 4 IF OBJECT_ID('Student','U') IS NOT NULL

 5 DROP TABLE Student

 6 GO

 7 

 8 CREATE TABLE Student

 9 (

10     StuID NVARCHAR(8) PRIMARY KEY,

11     Name NVARCHAR(5) 

12 )

13 GO

14 

15 INSERT INTO Student(StuID,Name) VALUES('20080001','Lily')

16 INSERT INTO Student(StuID,Name) VALUES('20080002','Lucy')

17 INSERT INTO Student(StuID,Name) VALUES('20080003','Jack')

18 GO

19 --------------------------------------------------------------------------

20 IF OBJECT_ID('SltCourse','U') IS NOT NULL

21 DROP TABLE SltCourse

22 GO

23 

24 CREATE TABLE SltCourse    --SelectiveCourse

25 (

26     ID INT PRIMARY KEY IDENTITY(1,1),

27     StuID NVARCHAR(8),

28     CourseName NVARCHAR(10),

29     Score    INT 

30 )

31 GO

32 

33 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080003','电脑维修',90)

34 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080003','剪纸',80)

35 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080003','市场策划',95)

36 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080003','信息检索',100)

37 

38 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080001','插花',99)

39 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080001','剪纸',96)

40 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080001','刺绣',92)

41 

42 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080002','插花',98)

43 GO

44 --------------------------------------------------------------------------

45 SELECT * FROM Student

46 GO

47 SELECT * FROM SltCourse

48 GO

49 --------------------------------------------------------------------------

50 SELECT * FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid

51 GO

52 --------------------------------------------------------------------------

53 WITH ReportCard 

54 AS(

55 SELECT s.StuID,s.Name,sc.CourseName,sc.Score FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid

56 )

57 SELECT  CASE WHEN RowNum=1 THEN StuID   ELSE '' END AS ID,

58         CASE WHEN RowNum=1 THEN Name    ELSE '' END AS Name,

59         CourseName,

60         Score

61 FROM (SELECT *,ROW_NUMBER()  OVER (PARTITION BY StuID,Name ORDER BY Score) AS RowNum FROM ReportCard) TBL

62 GO

63 --------------------------------------------------------------------------

64 DROP TABLE Student

65 GO

66 DROP TABLE SltCourse

67 GO

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然而……（然而……）×N

假如说，有一个字段是DateTime类型，那么可能会出现类似“1900-01-01 00:00:00.000”的东西。

例如下面略微修改过的代码，添加了入学时间（EntranceTime）：

 1 USE tempdb

 2 GO

 3 --------------------------------------------------------------------------

 4 IF OBJECT_ID('Student','U') IS NOT NULL

 5 DROP TABLE Student

 6 GO

 7 

 8 CREATE TABLE Student

 9 (

10     StuID NVARCHAR(8) PRIMARY KEY,

11     Name NVARCHAR(5),

12     EntranceTime DATETIME

13 )

14 GO

15 

16 INSERT INTO Student(StuID,Name,EntranceTime) VALUES('20080001','Lily','2008-08-27')

17 INSERT INTO Student(StuID,Name,EntranceTime) VALUES('20090002','Lucy','2009-08-26')

18 INSERT INTO Student(StuID,Name,EntranceTime) VALUES('20070003','Jack','2007-08-28')

19 GO

20 --------------------------------------------------------------------------

21 IF OBJECT_ID('SltCourse','U') IS NOT NULL

22 DROP TABLE SltCourse

23 GO

24 

25 CREATE TABLE SltCourse    --SelectiveCourse

26 (

27     ID INT PRIMARY KEY IDENTITY(1,1),

28     StuID NVARCHAR(8),

29     CourseName NVARCHAR(10),

30     Score    INT 

31 )

32 GO

33 

34 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20070003','电脑维修',90)

35 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20070003','剪纸',80)

36 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20070003','市场策划',95)

37 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20070003','信息检索',100)

38 

39 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080001','插花',99)

40 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080001','剪纸',96)

41 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20080001','刺绣',92)

42 

43 INSERT INTO SltCourse(StuID,CourseName,Score) VALUES('20090002','插花',98)

44 GO

45 --------------------------------------------------------------------------

46 SELECT * FROM Student

47 GO

48 SELECT * FROM SltCourse

49 GO

50 --------------------------------------------------------------------------

51 SELECT * FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid

52 GO

53 --------------------------------------------------------------------------

54 WITH ReportCard 

55 AS(

56 SELECT s.StuID,s.Name,s.EntranceTime,sc.CourseName,sc.Score FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid

57 )

58 SELECT  CASE WHEN RowNum=1 THEN StuID         　ELSE '' END AS ID,

59         CASE WHEN RowNum=1 THEN Name            ELSE '' END AS Name,

60         CASE WHEN RowNum=1 THEN EntranceTime    ELSE '' END AS EntranceTime,

61         CourseName,

62         Score

63 FROM (SELECT *,ROW_NUMBER()  OVER (PARTITION BY StuID,Name,EntranceTime ORDER BY Score) AS RowNum FROM ReportCard) TBL

64 GO

65 --------------------------------------------------------------------------

66 DROP TABLE Student

67 GO

68 DROP TABLE SltCourse

69 GO

最终显示为：

这肯定不行啊。

让我先想想。

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改成

WITH ReportCard 

AS(

SELECT s.StuID,s.Name,s.EntranceTime,sc.CourseName,sc.Score FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid

)

SELECT  CASE WHEN RowNum=1 THEN StuID         　ELSE '' END AS ID,

        CASE WHEN RowNum=1 THEN Name            ELSE '' END AS Name,

        CASE WHEN RowNum=1 THEN EntranceTime    ELSE cast(nullif('','') as datetime) END AS EntranceTime,

        CourseName,

        Score

FROM (SELECT *,ROW_NUMBER()  OVER (PARTITION BY StuID,Name,EntranceTime ORDER BY Score) AS RowNum FROM ReportCard) TBL

GO

则效果为

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但是怎么才能把变成呢？