题解 | 找出每个学校GPA最低的同学

select u.device_id,u.university,u.gpa
from user_profile u 
inner join
(select university,min(gpa) as min_gpa from user_profile group by university) t  # min(gpa)需要别名使用
on 
u.university = t.university and u.gpa = t.min_gpa
order by university

-- 子查询

SELECT a.device_id

,a.university

,a.gpa

from user_profile a

where gpa in (

select min(b.gpa)

from user_profile b

where a.university = b.university )