SELECT U.device_id, U.university, SUM(IF(Q.question_id IS NOT NULL, 1, 0)) AS question_cnt, SUM(IF(Q.result = 'right', 1, 0)) AS right_question_cnt FROM user_profile AS U LEFT JOIN question_practice_detail AS Q ON U.device_id = Q.device_id AND MONTH(date) = 08 WHERE ...