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

Often you use constraints in a database to ensure data to be "unique" in the data-based sense.

Regarding "isomorphisms" I think you are on your own, ie writing the code your self. If in the database you could use a trigger.