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 , qd.difficult_level, round(count(u.answer_cnt) / count(distinct u.device_id),4 ) avg_answer_cnt from user_profile as u, question_practice_detail as qpd ,question_detail as qd where qpd.device_id = u.device_id and qpd.question_id = qd.question_id group by u.university , qd.difficult_level;
-- 方式一 ：隐式内连接
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