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
with temp as (select exam_id
, date_format(start_time, '%Y%m') start_month
, count(1) as month_cnt
from exam_record
group by exam_id, start_month)
select exam_id
, start_month
, month_cnt
, sum(month_cnt) over (partition by exam_id order by start_month) as cum_exam_cnt
from temp;