Which customer has the most addresses?
customer refers to first_name, last_name; the most address refers to Max(count(address_id))
SELECT T1.first_name, T1.last_name FROM customer AS T1 INNER JOIN customer_address AS T2 ON T1.customer_id = T2.customer_id GROUP BY T1.first_name, T1.last_name ORDER BY COUNT(T2.customer_id) DESC LIMIT 1