select
    D.DEPT_CODE
    ,DEPT_NAME
    ,ORDER_NO
    ,C.CUST_CODE
    ,CUST_NAME
    ,ORDER_AMT
from
    TBL_ORDERS as O
    inner join TBL_DEPT as D
        on O.DEPT_CODE=D.DEPT_CODE
    left outer join TBL_CUST as C
        on O.CUST_CODE=C.CUST_CODE
where
    exists(
        select DEPT_CODE
        from TBL_DEPT
        where TBL_DEPT.DEPT_CODE=O.DEPT_CODE
        )
order by
    D.DEPT_CODE asc
    ,ORDER_NO asc;