题解 | #统计每个学校的答过题的用户的平均答题数#
统计每个学校的答过题的用户的平均答题数
https://www.nowcoder.com/practice/88aa923a9a674253b861a8fa56bac8e5
SELECT university, COUNT(*) / COUNT(DISTINCT qpd.device_id) FROM user_profile JOIN question_practice_detail qpd USING (device_id) GROUP BY university ORDER BY university