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 *,#第二步：试卷内按日期排序累计试卷作答记录 sum(month_cnt) over(partition by exam_id order by start_month rows between unbounded preceding and current row) cum_exam_cnt from(#第一步：统计每个试卷各月的作答数 select exam_id,date_format(start_time,"%Y%m") start_month, count(exam_id) month_cnt from exam_record group by exam_id,start_month ) as 第一步的表;
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