首先是三張表， CNo對應(yīng)的是課程，在這里我就粘貼了。????????????

????????????????????????????? 主表

???????????????? 人名表

按照常規(guī)查詢

SELECT s.SName, c.CName,s2.SCgrade

? FROM S s INNER JOIN SC s2 ON s2.SNo = s.SNo INNER JOIN C c ON c.CNo = s2.CNo

那么結(jié)果是這樣的

?

但是這是橫表 不是我想看到的結(jié)果。

我們要看到這樣的結(jié)果：

那么怎么辦呢？

?? 第一種寫法：SELECT w.SName,

?? sum(case when? w.CNo= 1 then w.SCgrade?? ELSE 0 END) AS '語文',

??? sum(case? WHEN w.CNo =2 THEN? w.SCgrade? ELSE?? 0 END) AS '數(shù)學',

? sum(case when? w.CNo= 3 then w.SCgrade? ELSE? 0 END) AS '英語'

FROM

(SELECT s.SNo,s.SName, s2.CNo, s2.SCgrade? FROM s s INNER JOIN SC s2 ON s2.SNo = s.SNo WHERE s.SNo IN (SELECT c.SNo? FROM sc c GROUP BY c.SNo ))

AS w GROUP BY w.SName

??

? ?第二種寫法： SELECT s.SName,

?? sum(case when? s2.CNo= 1 then s2.SCgrade?? ELSE 0 END) AS '語文',

??? sum(case? WHEN s2.CNo =2 THEN? s2.SCgrade? ELSE?? 0 END) AS '數(shù)學',

? sum(case when? s2.CNo= 3 then s2.SCgrade? ELSE? 0 END) AS '英語'

FROM

?S s INNER JOIN SC s2 ON s2.SNo = s.SNo

INNER JOIN C c ON c.CNo = s2.CNo

?GROUP BY s.SNo,

?s.SName

轉(zhuǎn)載于:https://www.cnblogs.com/kgdxpr/archive/2012/05/02/2479472.html

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