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
http://www.nowcoder.com/practice/f4714f7529404679b7f8909c96299ac4
select university,difficult_level,
round(count(q.question_id) / count(distinct u.device_id),4)
from question_practice_detail q left join user_profile u on u.device_id = q.device_id
left join question_detail d on q.question_id = d.question_id
group by university,difficult_level having university = '山东大学';
round(count(q.question_id) / count(distinct u.device_id),4)
from question_practice_detail q left join user_profile u on u.device_id = q.device_id
left join question_detail d on q.question_id = d.question_id
group by university,difficult_level having university = '山东大学';
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