MySQL的 - 2列

Question

组由结果通过SUM我有3个表：

user(id, name, id_school) 
school(id, name) 
result(id_user, stage1, stage2) 

现在我想获得学校的排名 - 是2列的总和：stage1和stage2所有用户。

Answer 1

试试这个查询。它只是assumption.please提供一些数据进行测试

SELECT 
    s.id, 
    s.name AS SchoolName 
    (r.S1 + r.S2) AS Rank 
FROM school as s 
LEFT JOIN user as u ON u.id_school = s.id 
LEFT JOIN (SELECT id_user , SUM(stage1) as S1 , SUM(stage2) FROM result GROUP BY id_user) as r ON r.id_user = u.id 
GROUP BY s.id 
ORDER BY Rank DESC 

Answer 2

我会做这样的事情：

SELECT school.name, SUM(result.result1 + result.result2) 
FROM school LEFT JOIN user ON (user.id_school = school.id) LEFT JOIN result ON (result.id_user = user.id) GROUP BY school.id 

希望它能帮助，祝你好运:)

Answer 3

显得过于简单：

select s.name as school, sum(stage1)+sum(stage2) as rank 
    from result r 
    join user u on u.id=r.id_user 
    join school s on s.id=u.id_school 
group by s.id 

我真的希望你有索引。