"all" in dropdown not working for query

I have a dropdown that is populated by the following query - but it
doesn't do what I want.

SELECT DISTINCT [Division group cross table].Division
FROM [Division group cross table] UNION select '(All)' from [division
group cross table]
ORDER BY [Division group cross table].Division;

I want the "all" part of it to remove the restrictive criteria. I have
seen some postings that tell you to use another column that is
invisible to the user. How do I add this other column to this query?