题解 | #浙大不同难度题目的正确率#

select d.difficult_level,sum(if(q.result='right',1,0))/count(result) as correct_rate
from question_practice_detail q left join user_profile u on q.device_id = u.device_id left join question_detail d on 
q.question_id = d.question_id
where u.university = '浙江大学'
group by d.difficult_level
order by correct_rate