who has the most orders? | Do you want just the customer name? | yes
SELECT T1.customer_name FROM customers AS T1 JOIN orders AS T2 ON T1.customer_id   =   T2.customer_id GROUP BY T1.customer_id ORDER BY count ( * )  DESC LIMIT 1
most orders refers to MAX(COUNT(order_id)); customer name refers to customer_name; joining customers with orders on customer_id to count orders per customer;