Database: customers_card_transactions
Question: What are the ids and full names of customers who hold two cards?
SQL: select t1.customer_id ,  t2.customer_first_name ,  t2.customer_last_name from customers_cards as t1 join customers as t2 on t1.customer_id  =  t2.customer_id group by t1.customer_id having count(*)  =  2