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(max(last_day(submit_time))),3) as avg_day_q_cnt
from practice_record
where year(submit_time) = '2021'
group by submit_month
)

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 asc