题解 | #每份试卷每月作答数和截止当月的作答总数。#

with zb as (select exam_id,date_format(start_time,'%Y%m') start_month,count(uid) month_cnt
from exam_record e1
group by exam_id,date_format(start_time,'%Y%m'))
select *,sum(month_cnt) over(partition by exam_id order by start_month) cum_exam_cnt
from zb