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
① select up.university, qd.difficult_level, round( count(qpd.question_id) / count(distinct qpd.device_id), 4 ) as avg_answer_cnt from question_practice_detail as qpd inner join user_profile as up on up.device_id = qpd.device_id and up.university = '山东大学' inner join question_detail as qd on qd.question_id = qpd.question_id group by qd.difficult_level; ② SELECT up.university, qd.difficult_level, round( COUNT(qpd.device_id) / COUNT(DISTINCT qpd.device_id), 4 ) AS avg_answer_cnt FROM user_profile up inner JOIN question_practice_detail qpd ON up.device_id = qpd.device_id inner JOIN question_detail qd ON qpd.question_id = qd.question_id GROUP BY up.university, qd.difficult_level HAVING up.university = '山东大学';