SELECT qd.difficult_level, ROUND(SUM(if(qpd.result = 'right',1,0))/count(qpd.device_id),4) AS correct_rate FROM user_profile up, question_practice_detail qpd, question_detail qd WHERE up.university= '浙江大学' AND up.device_id = qpd.device_id AND qpd.question_id = qd.question_id GROUP BY qd.difficult_le...