find duplicate addresses in database, stop users entering them early?

Question

How do I find duplicate addresses in a database, or better stop people already when filling in the form ? I guess the earlier the better?

Is there any good way of abstra

Answer 1

I realize that the original post is specif to German addresses, but this is a good questions for addresses in general.

In the United States, there is a part of an address called a delivery point barcode. It's a unique 12-digit number that identifies a single point of delivery and can serve as the unique identifier of an address. To get this value you'll want to use an address verification or address standardization web service API, which can cost about $20/mo depending upon the volume of requests you make to it.

In the interest of full disclosure, I'm the founder of SmartyStreets. We offer just such an address validation web service API called LiveAddress. You're more than welcome to contact me personally with any questions you have.