select
    DP.DEPT_CODE , DP.DEPT_NAME, OD.ORDER_NO, CS.CUST_CODE, CS.CUST_NAME, OD.ORDER_AMT 
from
    TBL_ORDERS as OD
    inner join TBL_DEPT as DP 
        ON DP.DEPT_CODE = OD.DEPT_CODE
    left outer join TBL_CUST as CS
        on CS.CUST_CODE = OD.CUST_CODE 
order by
    OD.DEPT_CODE asc
  , OD.ORDER_NO;