SQL 查询横表变竖表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
首先是三张表， CNo对应的是课程，在这里我就粘贴了。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：
代码如下:
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
第二种写法：
代码如下:
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。
