题解 | 统计加班员工占比

SELECT
    department,
    CONCAT(ROUND(count(a.first_clockin)/count(s.staff_id) * 100, 1),'%') as ratio
from
    staff_tb s
    left join 
    (   select *
        from attendent_tb
        where timestampdiff(second,first_clockin,last_clockin)/3600>9.5) a 
    on s.staff_id = a.staff_id
group by
    department
order by ratio desc