题解 | 月总刷题数和日均刷题数

select date_format(submit_time,'%Y%m') as submit_month,count(1) as month_q_cnt,round(count(1)/dayofmonth(last_day(max(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 all

select '2021汇总' as submit_month,count(1) as month_q_cnt,round(count(1)/31,3) as avg_day_q_cnt from practice_record
where year(submit_time) = 2021

order by submit_month