题解 | #统计每个学校各难度的用户平均刷题数#
统计每个学校各难度的用户平均刷题数
https://www.nowcoder.com/practice/5400df085a034f88b2e17941ab338ee8
SELECT
u.university,
d.difficult_level,
COUNT(d.question_id) / COUNT(DISTINCT q.device_id)
FROM
question_practice_detail q
LEFT JOIN user_profile u ON q.device_id = u.device_id
LEFT JOIN question_detail d ON q.question_id = d.question_id
GROUP BY
u.university,
d.difficult_level
