题解 | #浙大不同难度题目的正确率#

# 仿照上一题写的
select qd.difficult_level, sum(if(qpd.result = "right", 1, 0)) / count(qpd.question_id)  as correct_level
from question_practice_detail as qpd

left join question_detail as qd
    on qd.question_id = qpd.question_id
    
where qpd.device_id in(
    select device_id 
    from user_profile
    where university = "浙江大学"
)
group by qd.difficult_level
order by correct_level