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 t1 as ( select exam_id, date_format(start_time,'%Y%m') as start_month, count(start_time) as month_cnt FROM exam_record group by exam_id,start_month ) select *,sum(month_cnt) over(partition by exam_id order by start_month) from t1
