题解 | #每份试卷每月作答数和截止当月的作答总数。#

每份试卷每月作答数和截止当月的作答总数。

https://www.nowcoder.com/practice/5f1cbe74c682485aa73e4c2b30f04a62

select
exam_id,
date_format(start_time,"%Y%m") as month,
count(id),
sum(count(id))over(partition by exam_id order by date_format(start_time,"%Y%m") )
from exam_record 
group by exam_id,month

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