题解 | #统计每个学校各难度的用户平均刷题数#
统计每个学校各难度的用户平均刷题数
https://www.nowcoder.com/practice/5400df085a034f88b2e17941ab338ee8
select u.university, d.difficult_level, round(count(q.question_id)/count(distinct(q.device_id)) ,4) as avg_answer_cnt
from user_profile as u,question_practice_detail as q,question_detail as d
where u.device_id=q.device_id and q.question_id=d.question_id
group by u.university,d.difficult_level
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