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,
qd.difficult_level,
count(qpd.question_id)/count(distinct u.device_id) avg_answer_cnt
from
user_profile u
left join
question_practice_detail qpd
on u.device_id =qpd.device_id
join question_detail qd on qpd.question_id = qd.question_id
group by
u.university,
qd.difficult_level
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