Group by的用法

sql语句中的执行顺序:

from-> where -> join ->  group by -> having ->select ->order by ->limit

group by之后，

select语句能够写的字段只有三种

1）group by的字段

2）聚合函数 sum count...

3) 常量值

例如：错误的写法，brand，model属性无法进行查询

select
mid_id,
brand,
model,
count(*) login
from dwd_start_log
group by mid_id;

纠正：

select
mid_id,
brand,
model,
count(*) login
from dwd_start_log
group by mid_id,brand,model;