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 a ,
    (
        select
            university,
            min(gpa) as gpa
        from
            user_profile
        group by
            university
    ) b
where
    a.gpa = b.gpa and a.university = b.university
    order by a.university