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
*,
sum(month_cnt) over (
partition by
exam_id
order by
start_month
)
from
(
select
exam_id,
date_format (start_time, "%Y%m") as start_month,
count(1) as month_cnt
from
exam_record
group by
exam_id,
date_format (start_time, "%Y%m")
) a
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