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?? SQL語句行列轉換兩種方法 case ...when 和pivot函數(shù)應用SQL語句行列轉換兩種方法 case ...when
和pivot函數(shù)應用，運用pivot 函數(shù)只支持數(shù)據(jù)庫版本2005以上的。一般運用case? when else end 的方法
比較多，比較普遍。

?/*創(chuàng)建數(shù)據(jù)庫*/
?CREATE DATABASE tmp
?go
?USE tmp
?go

? /*創(chuàng)建數(shù)據(jù)庫測試表*/

CREATE TABLE [Scores]
???? (
?????? [ID] INT IDENTITY(1, 1)
??????????????? PRIMARY KEY ,
?????? [Student] VARCHAR(20) ,
?????? [Subject] VARCHAR(30) ,
?????? [Score] FLOAT
???? )

go

TRUNCATE TABLE Scores
?/*插入數(shù)據(jù)庫測試數(shù)據(jù)信息*/
??INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test001', '語文', '90' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test001', '英語', '85' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'text002', '語文', '90' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'text002', '英語', '80' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test003', '語文', '95' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test003', '英語', '85' )

/*1.? case when .......then else? ....end 用法，行列轉換*/
?SELECT? Student AS '姓名' ,
???????? MAX(CASE Subject
?????????????? WHEN '語文' THEN Score
?????????????? ELSE 0
???????????? END) AS '語文' ,--如果這個行是“語文”，就選此行作為列
??????? MAX(CASE Subject
?????????????? WHEN '英語' THEN Score
?????????????? ELSE 0
???????????? END) AS '英語'
FROM??? Scores
?GROUP BY Student
?ORDER BY Student

/*2. pivot(聚合函數(shù)(要轉成列值的列名)
　????? for 要轉換的列
?　　??? in（目標列名）
?　　)*/

SELECT? Student AS '姓名' ,
???????? AVG(語文) AS '語文' ,
???????? AVG(英語) AS '英語'
FROM??? Scores PIVOT( AVG(Score) FOR Subject IN ( 語文, 英語 ) )as NewScores
?GROUP BY Student
?ORDER BY Student ASC

???

?

轉載于:https://my.oschina.net/liangjw0504/blog/151736

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