SQL查询横表变竖表简析

首先是三张表， CNo对应的是课程，在这里我就粘贴了。

www.2cto.com

主表

人名表

按照常规查询

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

那么结果是这样的

但是这是横表 不是我想看到的结果。

我们要看到这样的结果：

那么怎么办呢？

第一种写法：SELECT w.SName,

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

sum(case WHEN w.CNo =2 THEN w.SCgrade ELSE 0 END) AS '数学',

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

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 www.2cto.com

第二种写法： SELECT s.SName,

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

sum(case WHEN s2.CNo =2 THEN s2.SCgrade ELSE 0 END) AS '数学',

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

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

这是我工作遇到过得情况，总结下来。如果有遇到这种情况的话可以参考下。

作者 小马的酒吧