select qd.difficult_level, sum(if(qpd.result = 'right',1,0))/ count(*) as correct_rate from user_profile up inner join question_practice_detail qpd on up.device_id = qpd.device_id inner join question_detail qd on qd.question_id = qpd.question_id where up.university = '浙江大学' group by qd.difficult_lev...