I want to know the customer names and how many credit cards they have?
SELECT T2.customer_first_name, T2.customer_last_name, count ( * )  FROM Customers_cards AS T1 JOIN Customers AS T2 ON T1.customer_id   =   T2.customer_id WHERE T1.card_type_code   =   "Credit" group by T1.customer_id
customer names refer to customer_first_name and customer_last_name; how many credit cards they have refers to COUNT(*) of credit card entries per customer; joining Customers_cards and Customers tables on customer_id to match credit card records with customer names; filtering for card_type_code = 'Credit' to consider only credit cards;