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
university,
difficult_level,
count(qpd.question_id) / count(DISTINCT qpd.device_id) as avg_answer_cnt
from
user_profile as u,
question_practice_detail as qpd,
question_detail as q
where
u.device_id = qpd.device_id
and
qpd.question_id = q.question_id
group by
university,difficult_level;
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