Question: What are the ids and first names of customers who do not hold a credit card?
SQL: SELECT customer_id ,  customer_first_name FROM Customers EXCEPT SELECT T1.customer_id ,  T2.customer_first_name FROM Customers_cards AS T1 JOIN Customers AS T2 ON T1.customer_id  =  T2.customer_id WHERE card_type_code  =  "Credit"