题解 | #月总刷题数和日均刷题数#

(
    select
        submit_month,
        question_total,
        round(question_total / days_in_month, 3)
    from
        (
            select
                date_format (submit_time, '%Y%m') submit_month,
                count(question_id) question_total,
                DAY (LAST_DAY (submit_time)) days_in_month
            from
                practice_record
            where
                year (submit_time) = '2021'
            group by
                submit_month,
                days_in_month
            order by
                submit_month asc
        ) a
)
union all
(
    select
        '2021汇总',
        count(question_id) question_total,
        round(count(question_id) / 31, 3)
    from
        practice_record
    where
        year (submit_time) = '2021'
    group by
        '2021汇总'
)