题解 | 统计加班员工占比

select
    department,
    concat(
        round(
                sum(
                    if(timestampdiff(second,at.first_clockin,at.last_clockin) /  3600> 9.5,1,0)
                ) / count(department) * 100
            ,1
        )
        ,'%'
    ) as ratio
from staff_tb st
 join attendent_tb at USING (staff_id)
group by department
order by ratio DESC