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(*)/day(last_day(max(date(submit_time)))),3) as avg_day_q_cnt
from practice_record
where year(submit_time)=2021
group by date_format(submit_time,'%Y%m') 

union

select '2021汇总' as submit_month,
count(*) as month_q_cnt,
round(count(*)/31,3) as avg_day_q_cnt
from practice_record
where year(submit_time)=2021
order by submit_month