> But that's not true. The problem being described is not caused or implied by a one-to-many relationship between customers and addresses. The actual problem is

> But that's not true. The problem being described is not caused or implied by a one-to-many relationship between customers and addresses. The actual problem is that the address table has unique constraints defined in such a way that duplicate addresses are not allowed. Furthermore the unique constraint most likely didn't even serve its purpose: How can you really make sure that an address is unique? There are countless ways to write one and the same address - in its simplest form it might be variations of Street / Str. or Avenue / Ave. Any information combining multiple lengthy strings will be prone to resulting in several slightly different variations.