题解 | 统计每个学校的答过题的用户的平均答题数
select
up.university,
round(
count(qpd.question_id) / count(distinct up.device_id),
4
) as avg_answer_cnt
from
user_profile as up
inner join question_practice_detail as qpd on up.device_id = qpd.device_id
group by
up.university
order by
up.university asc
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