SELECT ODR.DEPT_CODE, DEP.DEPT_NAME 
FROM TBL_ORDERS AS ODR
LEFT OUTER JOIN TBL_DEPT AS DEP
    ON DEP.DEPT_CODE = ODR.DEPT_CODE
UNION
SELECT SAL.DEPT_CODE, DEP.DEPT_NAME
FROM TBL_SALES AS SAL
LEFT OUTER JOIN TBL_DEPT AS DEP
    ON DEP.DEPT_CODE = SAL.DEPT_CODE
ORDER BY ODR.DEPT_CODE;