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?? SQL語(yǔ)句行列轉(zhuǎn)換兩種方法 case ...when 和pivot函數(shù)應(yīng)用SQL語(yǔ)句行列轉(zhuǎn)換兩種方法 case ...when
和pivot函數(shù)應(yīng)用，運(yùn)用pivot 函數(shù)只支持?jǐn)?shù)據(jù)庫(kù)版本2005以上的。一般運(yùn)用case? when else end 的方法
比較多，比較普遍。

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

? /*創(chuàng)建數(shù)據(jù)庫(kù)測(cè)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(kù)測(cè)試數(shù)據(jù)信息*/
??INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test001', '語(yǔ)文', '90' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test001', '英語(yǔ)', '85' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'text002', '語(yǔ)文', '90' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'text002', '英語(yǔ)', '80' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test003', '語(yǔ)文', '95' )
?INSERT? INTO Scores
???????? ( Student, Subject, Score )
?VALUES? ( 'test003', '英語(yǔ)', '85' )

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

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

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

???

?

轉(zhuǎn)載于:https://my.oschina.net/liangjw0504/blog/151736

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