query: SELECT customer_id ,  count(*) FROM Customers_cards GROUP BY customer_id
question: Show all customers id and number card owned by each customers.
query_toks: SELECT customer_id , count ( * ) FROM Customers_cards GROUP BY customer_id
query_toks_no_value: select customer_id , count ( * ) from customers_cards group by customer_id
question_toks: Show all customers id and number card owned by each customers.