SELECT dep.DEPT_NAME
    ,dep.DEPT_CODE
FROM TBL_ORDERS AS ord
JOIN TBL_SALES AS sal
ON ord.DEPT_CODE = sal.DEPT_CODE

LEFT OUTER JOIN TBL_DEPT AS dep
ON sal.DEPT_CODE = dep.DEPT_CODE
GROUP BY ord.DEPT_CODE
    ,dep.DEPT_NAME
ORDER BY dep.DEPT_CODE;