SQL33 Find the student with the lowest GPA in each school

Knowledge point: Pitfalls of group by

Original question link
description
Title: Now the operation wants to find the students with the lowest GPAs in each school for research. Please take out the lowest GPAs in each school.

Wrong answer:

SELECT device_id,university,MIN(gpa)
FROM user_profile
GROUP BY university 
ORDER BY university 

Writing this way will report an error:

“Expression #1 of SELECT list is not in GROUP BY clause and contains nonaggregated column ‘user_profile.device_id’ which is not functionally dependent on columns in GROUP BY clause; this is incompatible with sql_mode=only_full_group_by”

The reason is that it violates the only_full_group_by principle. If you are doing your own project, of course you can change the configuration of MySQL to solve this problem. But now you are doing a question and you cannot modify the configuration of Niuke, so to put it bluntly, you are not allowed to use this question. Answer this way

[The pitfall of group by]
使用group by之后select 语句中不能出现常数、聚合函数、聚合键以外的字段, device_id is a field other than..., so an error occurred

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The correct answer to this question:

select
  device_id,
  university,
  gpa
from
  user_profile
where
  (university, gpa) in (
    select
      university,
      min(gpa)
    from
      user_profile
    group by
      university
  )
order by
  university