行列转换
要用到SQL SERVER
CASE [字段名] WHEN ‘字段名’ THEN [字段的数据值] ELSE 0 END
CASE WHEN [字段名] = ‘字段名’ THEN [字段的数据值] ELSE 0 END
判断一个字段名是否和这个改字段名相等，如果相等，就得到字段的数据值，否则为0.
Student
| uid （key) | name | age |
|---|
| 1 | 张三 | 22 |
| 2 | 李四 | 22 |
| 3 | 王五 | 19 |
score
| sid （key) | sname | score | uid |
|---|
| 1 | 数学 | 111 | 1 |
| 2 | 英语 | 122 | 1 |
| 3 | 语文 | 119 | 1 |
| 4 | 数学 | 121 | 2 |
| 5 | 英语 | 122 | 2 |
| 6 | 语文 | 123 | 2 |
| 7 | 数学 | 131 | 3 |
| 8 | 英语 | 142 | 3 |
| 9 | 语文 | 139 | 3 |
输出表格式
SELECT s3.uid,s3.age,s3.name,
SUM(CASE s3.sname WHEN '英语' THEN scores ELSE 0 END) AS '数学',
SUM(CASE s3.sname WHEN '数学' THEN scores ELSE 0 END) AS '英语',
SUM(CASE s3.sname WHEN '语文' THEN scores ELSE 0 END) AS '语文'
FROM (select s1.uid,s1.name,s1.age,sname,scores,sid from
dbo.student as s1,dbo.score as s2 where s1.uid = s2.uid) as s3
GROUP BY s3.uid,s3.age,s3.name;
