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
university,
difficult_level,
count(q.question_id) / count(distinct (u.device_id)) as avg_answer_cnt
from
user_profile as u
join question_practice_detail as q on u.device_id = q.device_id
join question_detail as d on q.question_id = d.question_id
where university = "山东大学"
group by difficult_level
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