题解 | #浙大不同难度题目的正确率#

select qde.difficult_level,count(if(qp.result='right',1,null))/count(qp.question_id) correct_rate
from (select device_id
from user_profile
where university='浙江大学') u 
join question_practice_detail qp on u.device_id=qp.device_id
join question_detail qde on qp.question_id=qde.question_id
group by qde.difficult_level
order by correct_rate;