select
    c.DEPT_CODE
    , a.DEPT_NAME 
from
    TBL_DEPT as a 
    right outer join TBL_ORDERS as b 
        on a.DEPT_CODE = b.DEPT_CODE
    right outer join TBL_SALES as c 
        on a.DEPT_CODE = c.DEPT_CODE
group by c.dept_code
order by c.dept_code asc