SELECT
    O.DEPT_CODE
    ,D.DEPT_NAME
FROM
    TBL_ORDERS AS O
LEFT OUTER JOIN
    TBL_DEPT AS D
  ON
    O.DEPT_CODE = D.DEPT_CODE

UNION

SELECT
    S.DEPT_CODE
    ,D.DEPT_NAME
FROM
    TBL_SALES AS S
LEFT OUTER JOIN
    TBL_DEPT AS D
  ON
    S.DEPT_CODE = D.DEPT_CODE
    
ORDER BY
    O.DEPT_CODE ASC
    ,S.DEPT_CODE ASC;