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
http://www.nowcoder.com/practice/f4714f7529404679b7f8909c96299ac4
SELECT university, q2.difficult_level, count(q1.question_id)/count(DISTINCT u.device_id) from user_profile u inner join question_practice_detail q1 on u.device_id = q1.device_id inner join question_detail q2 ON q2.question_id = q1.question_id where u.university = '山东大学' group by q2.difficult_level;
团结起来
