I am also interested in finding out about protecting a database solution. Did you find out any useful information?
I'm not a lawyer, you would need to contact a lawyer to be certain. As a developer of software and according to research I've done. Software can be copyrighted. Most programming languages are created with other languages such as c. Databases would fall in this same category. Filemaker has a license agreement and you would have a agreement for your databases / app which would protect your work.
By the way, you can copyright anything without a lawyer by simply displaying this message in a splash screen....
All Rights Reserved!