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

Before you start searching for duplicate addresses in your database, you should first make sure you store the addresses in a standard format.

Most countries have a standard way of formatting addresses, in the US it's the USPS CASS system: http://www.usps.com/ncsc/addressservices/certprograms/cass.htm

But most other countries have a similar service/standard. Try this site for more international formats: http://bitboost.com/ref/international-address-formats.html

This not only helps in finding duplicates, but also saves you money when mailing you customers (the postal service charges less if the address is in a standard format).

Depending on your application, in some cases you might want to store a "vanity" address record as well as the standard address record. This keeps your VIP customers happy. A "vanity" address might be something like:

62 West Ninety First Street
Apartment 4D
Manhattan, New York, NY 10001

While the standard address might look like this:

62 W 91ST ST APT 4D
NEW YORK NY 10024-1414