TBL_DEPT AS DP
 TBL_CUST AS CS
 TBL_ORDERS AS OD

 SELECT * FROM DP
 FULL JOIN OD
 ON DP.DEPT_CODE = OD.DEPT_CODE
  
 SELECT * FROM CS
 RIGHT JOIN OD
 ON CS.CUST_CODE = OD.CUST_CODE
        
SELECT 
    DP.DEPT_CODE, 
    DP.DEPT_NAME, 
    OD.ORDER_NO, 
    CS.CUST_CODE, 
    CS.CUST_NAME, 
    OD.ORDER_AMT
FROM OD 

ORDER BY OD.DEPT_CODE ASC
         OD.ORDER_NO ASC