题解 | #从尾到头打印链表#

select DATE_FORMAT(submit_time,'%Y%m') submit_month ,count(uid) month_q_cnt ,round(count(uid)/ max(DAY(LAST_DAY(submit_time))),3) avg_day_q_cnt from practice_record where DATE_FORMAT(submit_time,'%Y') = '2021' and score is not null group by submit_month union all select '2021汇总' as submit_month,count(submit_time) as month_q_cnt, round(count(submit_time)/31,3) as avg_day_q_cnt from practice_record where DATE_FORMAT(submit_time,'%Y') = '2021' and score is not null group by submit_month order by submit_month