题解 | 月总刷题数和日均刷题数

select
    date_format(submit_time,'%Y%m') as submit_month,
    count(submit_time) as month_q_cnt,
    round(count(submit_time)/day(avg(last_day(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(submit_time) as month_q_cnt,
    round(count(submit_time)/31,3) as avg_day_q_cnt
from
    practice_record
where
    year(submit_time)=2021 

order by
    submit_month