ha questo:
$sql = "delete from address_book where email_address='".$email."' and password='".$password."' ";

$resource = mysql_query($sql) or die(mysql_error());

$res = mysql_affected_rows($resource);

echo "res: $res , resourse: $resource, sql:$sql";

mi da come risultato questo

res: , resourse: 1, sql:delete from address_book where email_address='pincopallino@hotmail.it' and password='killua85'

$res mi da niente