mysql联表分组求和

Question

1.求a表分组的分数 并排序

2.
a表
id
openid
groups 分组

b表
id
openid
step分数

openid是两表的关联字段

3.获取 groups分组 对应b表 step分数的和 按照groups排序结果

Answer 1

用 php 循环解决了

Answer 2

SELECT a.groups,SUM(b.step) FROM a INNER JOIN b USING (openid) GROUP BY a.groups ORDER BY a.groups DESC

Answer 3

SELECT a.id,a.groups,sum(b.step)as score FROM a LEFT JOIN b ON a.groups=b.groups GROUP BY a.groups