Database: customers_card_transactions
Question: Show the customer ids and firstname without a card with type code "Credit".
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"