220115

• one to many(일대다) 그리고 foreign key

CREATE TABLE customers(
    id INT AUTO_INCREMENT PRIMARY KEY,
    first_name VARCHAR(100),
    last_name VARCHAR(100),
    email VARCHAR(100)
);
CREATE TABLE orders(
    id INT AUTO_INCREMENT PRIMARY KEY,
    order_date DATE,
    amount DECIMAL(8,2),
    customer_id INT,
    FOREIGN KEY(customer_id) REFERENCES customers(id)
);

서브쿼리

SELECT * FROM orders WHERE customer_id =
    (
        SELECT id FROM customers
        WHERE last_name='George'
    );

• IMPLICIT INNER JOIN

SELECT * FROM customers, orders 
WHERE customers.id = orders.customer_id;

• EXPLICIT INNER JOIN

SELECT * FROM customers
JOIN orders
	ON customers.id = orders.customer_id;