Question: Show the card type codes and the number of transactions.
Schema: create table financial_transactions (card_id varchar, PRIMARY KEY (card_id)); create table customers_cards (card_type_code varchar, card_id varchar, PRIMARY KEY (card_type_code))
SQL: select t2.card_type_code, count(*) from financial_transactions as t1 join customers_cards as t2 on t1.card_id = t2.card_id group by t2.card_type_code