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 university,difficult_level,count(answer_cnt)/count(DISTINCT question_practice_detail.device_id) as avg_answer_cnt FROM user_profile,question_practice_detail,question_detail WHERE user_profile.device_id=question_practice_detail.device_id AND question_practice_detail.question_id=question_detail.question_id GROUP BY university,difficult_level ORDER BY university;
