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 u.university, d.difficult_level, COUNT(d.question_id) / COUNT(DISTINCT q.device_id) AS avg_answer_cnt 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 WHERE u.university = '山东大学' GROUP BY d.difficult_level