SELECT td.DEPT_CODE
    ,td.DEPT_NAME
    ,TBL_ORDERS.ORDER_NO
    ,tc.CUST_CODE
    ,tc.CUST_NAME
    ,TBL_ORDERS.ORDER_AMT
FROM TBL_ORDERS 
JOIN TBL_DEPT AS td
ON TBL_ORDERS.DEPT_CODE = td.DEPT_CODE

LEFT OUTER JOIN TBL_CUST AS tc
ON TBL_ORDERS.CUST_CODE = tc.CUST_CODE
ORDER BY td.DEPT_CODE
    ,TBL_ORDERS.ORDER_NO;