Query returns 2 results instead of 1

[icemac]

I am creating a database for a hyperthetical car hire company. A customer hires a car from and until a certain date. If a new customer decides to hire a car i want to generate a list of cars that he can choose on depending on the other dates from which other cars are hire from and until. I have created a query that generates all of the cars that the new customer can not use.
I have also generated a list of all of the cars, in the database.

I have created a new query takes the numberplates of all the cars and subtracts the numberplates of the cars that are being used.

This is where i hit a problem. For some reason the query is generating the list of number plates twice and then subtracting the numberplates that are being used. This leaves me with with 2 values for every numberplate that can be used and 1value for every numberplate that cannot be used. Can you help me?

Please post your email address so i can send you the zip file as the file is too large to upload. The query that i am having problems with has the title:SEARCH FOR AVAILIABLE CARS.

Thank You

 

[gemma-the-husky]

look at find unmatched queries in the query wizard.

 

[icemac]

Thank you that was lots of help