题解 | #找出每个学校GPA最低的同学#

select a.device_id, a.university, a.gpa
from user_profile as a
right join 
(
    select university , min(gpa) as gpa
    from  user_profile
    group by university
) as b
on a.university=b.university and a.gpa=b.gpa
order by a.university

right join ： 联结后的内容为左表和右表的交集+以及交集对应的右表的部分