What is the customer first, last name and id with the most number of accounts?
SELECT T2.customer_first_name ,  T2.customer_last_name ,  T1.customer_id FROM Accounts AS T1 JOIN Customers AS T2 ON T1.customer_id   =   T2.customer_id GROUP BY T1.customer_id ORDER BY count ( * )  DESC LIMIT 1
customer first, last name and id with the most number of accounts refers to selecting customer_first_name, customer_last_name, and customer_id from a JOIN between Accounts and Customers table, grouping by customer_id and ordering by COUNT(*) DESC to find the maximum number of accounts per customer.