SELECT 
[D].DEPT_CODE
,[D].DEPT_NAME
,[O].ORDER_NO
,[C].CUST_CODE
,[C].CUST_NAME
,[O].ORDER_AMT
FROM
TBL_ORDERS AS [O]
LEFT JOIN
TBL_DEPT AS [D]
ON  [O].DEPT_CODE == [D].DEPT_CODE
LEFT JOIN
TBL_CUST AS [C]
ON [O].CUST_CODE == [C].CUST_CODE
WHERE
[D].DEPT_CODE IS NOT NULL AND [C].CUST_CODE IS NOT NULL
ORDER BY
[D].DEPT_CODE ASC ,[O].ORDER_NO ASC