select
  device_id,
  university,
  gpa
from
(
    select
      *,
      rank() over (
        partition by university
        order by
          gpa
      ) as rk
    from
      user_profile
  ) as my_min
where
  rk = 1

虽然用子查询gpa=min(xxx)的方式也可以，但是窗口函数效率更高