select
    b.staff_id,
    a.staff_name,
    concat (
        round(
            sum(b.dock_salary) / sum(b.normal_salary) * 100,
            1
        ),
        '%'
    ) as dock_ratio
from
    salary_tb b
    left join staff_tb a on a.staff_id = b.staff_id
where
    a.department = 'dep1'
group by
    b.staff_id,
    a.staff_name
order by dock_ratio desc