题解 | #浙大不同难度题目的正确率#

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