Question: What dates did they become customers?
SQL: SELECT t1.customer_name, T1.date_became_customer FROM customers AS t1 JOIN customer_orders AS t2 ON t1.customer_id   =   t2.customer_id JOIN order_items AS t3 ON t2.order_id   =   t3.order_id WHERE t3.order_quantity   =    (  SELECT max ( order_quantity )  FROM order_items )