CREATE TABLE Accounts (account_id NUMBER, customer_id NUMBER, account_name VARCHAR2, other_account_details VARCHAR2)
CREATE TABLE Customers_Cards (card_id NUMBER, customer_id NUMBER, card_type_code VARCHAR2, card_number VARCHAR2, date_valid_from DATETIME, date_valid_to DATETIME, other_card_details VARCHAR2)
CREATE TABLE Financial_Transactions (transaction_id NUMBER, previous_transaction_id NUMBER, account_id NUMBER, card_id NUMBER, transaction_type VARCHAR2, transaction_date DATETIME, transaction_amount DOUBLE PRECISION, transaction_comment VARCHAR2, other_transaction_details VARCHAR2)
CREATE TABLE Customers (customer_id NUMBER, customer_first_name VARCHAR2, customer_last_name VARCHAR2, customer_address VARCHAR2, customer_phone VARCHAR2, customer_email VARCHAR2, other_customer_details VARCHAR2)

Show the number of customers for different customer last name in a bar chart.
SELECT customer_last_name, COUNT(customer_last_name) FROM Customers GROUP BY customer_last_name
SELECT "customer_last_name", COUNT("customer_last_name") FROM "Customers" GROUP BY "customer_last_name"