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[数据库]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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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 GO14 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 GO19 --------------------------------------------------------------------------20 IF OBJECT_ID('SltCourse','U') IS NOT NULL21 DROP TABLE SltCourse22 GO23 24 CREATE TABLE SltCourse  --SelectiveCourse25 (26   ID INT PRIMARY KEY IDENTITY(1,1),27   StuID NVARCHAR(8),28   CourseName NVARCHAR(10),29   Score  INT 30 )31 GO32 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 GO44 --------------------------------------------------------------------------45 SELECT * FROM Student46 GO47 SELECT * FROM SltCourse48 GO49 --------------------------------------------------------------------------50 SELECT * FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid51 GO52 --------------------------------------------------------------------------53 WITH ReportCard 54 AS(55 SELECT s.StuID,s.Name,sc.CourseName,sc.Score FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid56 )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     Score61 FROM (SELECT *,ROW_NUMBER() OVER (PARTITION BY StuID,Name ORDER BY Score) AS RowNum FROM ReportCard) TBL62 GO63 --------------------------------------------------------------------------64 DROP TABLE Student65 GO66 DROP TABLE SltCourse67 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 DATETIME13 )14 GO15 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 GO20 --------------------------------------------------------------------------21 IF OBJECT_ID('SltCourse','U') IS NOT NULL22 DROP TABLE SltCourse23 GO24 25 CREATE TABLE SltCourse  --SelectiveCourse26 (27   ID INT PRIMARY KEY IDENTITY(1,1),28   StuID NVARCHAR(8),29   CourseName NVARCHAR(10),30   Score  INT 31 )32 GO33 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 GO45 --------------------------------------------------------------------------46 SELECT * FROM Student47 GO48 SELECT * FROM SltCourse49 GO50 --------------------------------------------------------------------------51 SELECT * FROM Student s,SltCourse sc WHERE s.stuid=sc.stuid52 GO53 --------------------------------------------------------------------------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.stuid57 )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     Score63 FROM (SELECT *,ROW_NUMBER() OVER (PARTITION BY StuID,Name,EntranceTime ORDER BY Score) AS RowNum FROM ReportCard) TBL64 GO65 --------------------------------------------------------------------------66 DROP TABLE Student67 GO68 DROP TABLE SltCourse69 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,    ScoreFROM (SELECT *,ROW_NUMBER() OVER (PARTITION BY StuID,Name,EntranceTime ORDER BY Score) AS RowNum FROM ReportCard) TBLGO

则效果为

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但是怎么才能把变成呢?