题解 | 统计加班员工占比

select
    department,
    concat (
        round(
            count(
                if (
                    timestampdiff (minute, first_clockin, last_clockin) > (9.5 * 60),
                    1,
                    null
                )
            ) / count(st.staff_id) * 100,
            1
        ),
        '%'
    ) as ratio
from
    staff_tb st,
    attendent_tb at
where
    st.staff_id = at.staff_id
group by
    department
order by
    ratio desc