SELECT qd.difficult_level,SUM(if(qpd.result='right',1,0))/COUNT(qpd.device_id) AS corrct_rate FROM user_profile up JOIN question_practice_detail qpd ON up.device_id=qpd.device_id JOIN question_detail qd ON qpd.question_id=qd.question_id WHERE up.university='浙江大学' GROUP BY qd.difficult_level ORDER BY corrct_rate;