题解 | #找出每个学校GPA最低的同学#

由于聚合函数MIN()在GROUP BY 分组后将不能同步筛选出对应的device_id,university的信息，
需要通过row_number() over(partition by universtiy order by gpa)的窗口函数实现

SELECT device_id,
       university,
       gpa
FROM (select device_id,
             university,
             gpa,
             row_number() over(PARTITION BY university ORDER BY gpa) as rn
      from user_profile) as t
WHERE rn=1;