SELECT 
    DEP.DEPT_CODE
    ,DEPT_NAME
    ,ORDER_NO
    ,CUS.CUST_CODE
    ,CUST_NAME
    ,ORDER_AMT
FROM
    TBL_DEPT as DEP
    inner join TBL_ORDERS as ORD
    on DEP.DEPT_CODE = ORD.DEPT_CODE
    left join TBL_CUST as CUS
    on ORD.CUST_CODE = CUS.CUST_CODE
ORDER BY
    ORD.DEPT_CODE ASC,
    ORDER_NO ASC