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