I've gotta run right now, so I can't get into all the details, but try this instead:

SELECT
---PC.ProjectCode_Item_Code
FROM
---mwebProjectCode---PC---,
---mwebWork------------W
WHERE
---------PC.Work_Entity_Type---------=---3
---AND---PC.Work_ID------------------<> 2531
---AND---W.Work_Item_Code---------(+)=---PC.ProjectCode_Item_Code
---AND---W.Work_Level------------(+)=---6
---AND---W.Work_Item_Code------------IS---NULL
ORDER BY
---ProjectCode_Item_Code


HTH,

- Chris