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(qpd.question_id) / COUNT(DISTINCT qpd.device_id)
FROM user_profile up
JOIN question_practice_detail qpd USING (device_id)
JOIN question_detail qd USING (question_id)
WHERE university = '山东大学'
GROUP BY difficult_level
