题解 | #统计每个用户的平均刷题数#
统计每个用户的平均刷题数
https://www.nowcoder.com/practice/f4714f7529404679b7f8909c96299ac4
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
and u.university='山东大学'
group by d.difficult_level
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