题解 | #浙大不同难度题目的正确率#

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