select staff_id,staff_name,dock_ratio from
(
select st.staff_id as staff_id,staff_name,department,concat(round(dock_salary/normal_salary*100,1),'%') as dock_ratio from staff_tb as st
join
(
select staff_id, normal_salary, dock_salary from salary_tb
) as sa
on st.staff_id = sa.staff_id
where department = 'dep1'
order by dock_salary/normal_salary desc
) as t1