It's like I said. An address table instead of fields in the person table. That way you can store a single address one time. Then an interim table, a table that matches between the person table and the address table. It's also called a many-to-many table. It allows for a person to have more than one address. Which makes sense. You have a home address, a work address, possibly a shipping address, a billing address, etc. The interim table has in it the primary key from the person table and the primary key from the address table, which would probably be a system generated identifier, but it could be a natural key.