SELECT 
DE.DEPT_CODE,
DE.DEPT_NAME,
OE.ORDER_NO,
CU.CUST_CODE,
CU.CUST_NAME,
OE.ORDER_AMT
FROM  TBL_ORDERS AS OE
INNER JOIN TBL_DEPT AS DE ON DE.DEPT_CODE = OE.DEPT_CODE
LEFT OUTER JOIN TBL_CUST AS CU ON CU.CUST_CODE = OE.CUST_CODE
ORDER BY OE.DEPT_CODE ASC, OE.ORDER_NO;