题解 | #用户每月最后一周的练题数#
用户每月最后一周的练题数
https://www.nowcoder.com/practice/00fa10258481407b9a4b3f9a93703700
select device_id, date_format (event_date, '%Y年%m月') as ym, count(question_id) as cnt from question_practice_detail where datediff(last_day(event_date), event_date) < 7 group by device_id,ym order by device_id asc,ym asc
得到月份最后一天使用last_day()函数,日期进行减法,使用datediff()函数。