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(question_id) / count(distinct (device_id)) as avg_answer_cnt
from
user_profile
right join question_practice_detail using (device_id)
inner join question_detail using (question_id)
where
university = "山东大学"
group by
difficult_level
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