right join 是以u2表数据为基础去显示u2全部数据及u1表符合搜索条件的数据
select device_id
,u2.university
,u2.gpa
from user_profile u1
right join
 (select university,min(gpa) gpa
from user_profile 
group by university) u2
on 
u1.university=u2.university
and u1.gpa=u2.gpa
order by u1.university