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)
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 Accounts (account_id NUMBER, customer_id NUMBER, account_name VARCHAR2, other_account_details VARCHAR2)

Show all customer ids and the number of accounts for each customer. Show the correlation.
SELECT customer_id, COUNT(*) FROM Accounts GROUP BY customer_id
SELECT "customer_id", COUNT(*) FROM "Accounts" GROUP BY "customer_id"