SELECT
    TD.DEPT_CODE
    ,DEPT_NAME
    ,ORDER_NO
    ,TC.CUST_CODE
    ,ORDER_AMT
FROM
    TBL_ORDERS AS T
JOIN
    TBL_CUST AS TC
ON
    T.CUST_CODE = TC.CUST_CODE
LEFT JOIN 
    TBL_DEPT AS TD
ON
    T.DEPT_CODE = TD.DEPT_CODE
WHERE
    TD.DEPT_CODE IS NOT NULL
ORDER BY
    TD.DEPT_CODE,
    T.ORDER_NO