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 `university`,`difficult_level`,ROUND(COUNT(qpd.question_id)/COUNT(DISTINCT(qpd.device_id)),4) AS `avg_answer_cnt` FROM `user_profile` AS `up` JOIN `question_practice_detail` AS `qpd` ON `up`.`device_id`=`qpd`.`device_id` JOIN `question_detail` AS `qd` ON `qpd`.`question_id`=`qd`.`question_id` WHERE `university`='山东大学' GROUP BY `difficult_level`;
