SELECT university, difficult_level, ROUND( COUNT(qpd.question_id) / COUNT(distinct qpd.device_id) , 4) AS avg_answer_cnt FROM user_profile AS up INNER JOIN question_practice_detail AS qpd ON up.device_id = qpd.device_id INNER JOIN question_detail AS qd ON qpd.question_id = qd.question_id GROUP BY un...
