原文:
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？
