题解 | 找出每个学校GPA最低的同学

with a as (
    select device_id, university, gpa, row_number() over (partition by university order by gpa) as rnk from user_profile
)
select device_id, university, gpa
from a 
where rnk = 1

不知道不开窗行不行，我写出来报错