题解 | #月总刷题数和日均刷题数#

select date_format(submit_time,'%Y%m') as submit_month,
count(*) as month_q_cnt,
round(count(*) / max(day(last_day(submit_time))),3) as avg_day_q_cnt
from practice_record
where year(submit_time) = 2021
group by submit_month
union all
select '2021汇总',count(*),round(count(*) / 31,3)
from practice_record
where year(submit_time) = 2021
order by submit_month;