default addresses in addressbook

I am building an address book in MySQL with a many-to-many join.

Table 1:
name
id

Table 2:
email address
id

table 3:
table1.id
table2.id

If a person has more than one address, I want to add a field somewhere, probably in table 2 or 3, to specify that the certain email address is the default address. How would I implement this? How would I enforce that only one address per person would be default? What SQL would I need to retrieve only a default email address and not all addresses for a person?

Okay... why are you doing a many to many... how many cases are there going to be of the email address going to many names? Just do a one to many link.

Table 1
name_id
name

Table 2
email_id
name_id
email_address
default

Make the default a boolean field and have true to denote default address.

The SQL you need is

SELECT t1.name, t2.email_address FROM Table1 as t1, Table2 as t2 WHERE t1.name_id=t2.name_id AND t2.default='true'

This is why I don't like the windows address book. I started to make my own, but I came up with this problem.