Noobie Question: Being able to recognise the type of content in a form

[MortimerJazz]

I'm not sure that's the best title for my question, but it pretty much sums up something that I've been seeing on a few websites recently. Especially property sites.

If you look on something like [url=http://www.PropertyFinder.com]PropertyFinder[/url], they have a search box which asks you to "Enter a Property ID, Location or Postcode"

My question is, when a user hits the submit button, how does the processing script know which DB table to search through in order to get the relevant information. How does the processing script know whether the user has inputted an ID, a location or a postcode?

Thanks very much

[Cep]

The data from the form is passed back to the server where the script resides. It is processed by the script processor and somewhere within the code of that script it will connect to a database and query the information.