题解 | #浙大不同难度题目的正确率#

select
    difficult_level,
    round(sum(if(result='right',1,0))/count(question_id),4) as correct_rate
from user_profile u inner join question_practice_detail q
on u.device_id=q.device_id and u.university='浙江大学'
inner join question_detail qd
using (question_id)
group by difficult_level
order by correct_rate;

首先获取浙江大学的所有做题记录，其次获取每条做题记录的难易程度。