题解 | #浙大不同难度题目的正确率#

select qd.difficult_level,
  avg(if(qpd.result='right',1,0)) as correct_rate

from question_detail as qd
inner join question_practice_detail as qpd
on qd.question_id = qpd.question_id
inner join  user_profile as up
on up.device_id = qpd.device_id

where up.university = '浙江大学' 
group by qd.difficult_level
order by correct_rate asc