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,
any_value(round(count(*)/day(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(*) as month_q_cnt,
round(count(*)/31,3) as avg_day_q_cnt
from practice_record
where year(submit_time)=2021
group by date_format(submit_time,'%Y')
order by submit_month;

使用any_value()函数可以解决ONLY_FULL_GROUP_BY报错。

不使用该函数可以对day(last_day(submit_time))求avg或max，min

原因是day(last_day(submit_time))返回的是一个序列，而不是一个数

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