题解 | #浙大不同难度题目的正确率#
浙大不同难度题目的正确率
http://www.nowcoder.com/practice/d8a4f7b1ded04948b5435a45f03ead8c
select difficult_level,
round(sum(if(result="right",1,0))/count(result) ,4) as correct_rate
from(
select u.device_id ,result,question_id
from user_profile u
left join question_practice_detail q
using(device_id)
where university ="浙江大学") as t1
join question_detail
using(question_id)
group by difficult_level
order by correct_rate
round(sum(if(result="right",1,0))/count(result) ,4) as correct_rate
from(
select u.device_id ,result,question_id
from user_profile u
left join question_practice_detail q
using(device_id)
where university ="浙江大学") as t1
join question_detail
using(question_id)
group by difficult_level
order by correct_rate
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