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

Match address to addresses provided by DET BundesPost to detect duplicates.

DET probably sells a CD like USA does. The problem then becomes matching to the Bundespost addresses. Just a long process of replacing abbreviations with the post approved abbreviations and such.

Same way in USA. Match to USPostOffice addresses (Sorry these cost money so its not entirely open CDs are available from the US post office) to find duplicates.