题解 | #计算用户8月每天的练题数量#

SELECT
    EXTRACT(day from date) day,
    count(*) question_cnt
from question_practice_detail
where year(date) = 2021 and month(date) = 8
group by EXTRACT(day from date)

SELECT
    case when year(date) = 2021 and month(date) = 8
    then extract(day from date)
    else null end as day,
    count(*) question_cnt
from question_practice_detail
group by day
having day is not null

SELECT
    EXTRACT(day from date) day,
    COUNT(*) question_cnt
from question_practice_detail
where date in (
    select date from question_practice_detail
    where YEAR(date) = 2021 and MONTH(date) = 8)
group by day