Queries :: Union Query - Control Source For Unbound Listbox

I'm preparing a query as the control source for an unbound listbox. The following code gives the desired results:

Code:
SELECT DISTINCT tblCameras.CameraNum, QrySbfShotList.CamerasFK
FROM QrySbfShotList INNER JOIN tblCameras ON QrySbfShotList.CamerasFK = tblCameras.CamerasID
WHERE (((QrySbfShotList.shootsFK)=[my].[control]))
ORDER BY QrySbfShotList.CamerasFK

(My.control will be a control on the form. For the time being, I let the query prompt me for a value.)

It produces two columns like so:

CameraNum Camera ID
1 2
2 3
3 4
4 5
5 6
6 7
8 9
11 12

CameraNum is text; CameraID is numeric.

Now, I'm trying to use a trick I read about that should add a single textual entry to the top of the list like so:

Code:
SELECT DISTINCT tblCameras.CameraNum, QrySbfShotList.CamerasFK
FROM QrySbfShotList INNER JOIN tblCameras ON QrySbfShotList.CamerasFK = tblCameras.CamerasID
WHERE (((QrySbfShotList.shootsFK)=[my].[control]))
ORDER BY QrySbfShotList.CamerasFK

union

SELECT "(ALL)", "Dummy"
FROM QrySbfShotList INNER JOIN tblCameras ON QrySbfShotList.CamerasFK = tblCameras.CamerasID
WHERE (((QrySbfShotList.shootsFK)=[my].[control]));

This produces

CameraNum Camera ID
ALL Dummy
1 2
11 12
2 3
3 4
4 5
5 6
6 7
8 9

The second (numeric) column is now out of order. This is reproducible for other values of my.control. If there are double digit entries they get inserted at the third row.

Why? What am I not understanding about how UNION works?

(BTW, I know I could put the "ALL" entry into tblCameras, thereby avoiding the need for a union, but I'd still like to know why the unexpected result.)