natural_join.sql

-- table yaratrish
DROP TABLE IF EXISTS categories;
CREATE TABLE categories (
	category_id serial PRIMARY KEY,
	category_name VARCHAR (255) NOT NULL
);

DROP TABLE IF EXISTS products;
CREATE TABLE products (
	product_id serial PRIMARY KEY,
	product_name VARCHAR (255) NOT NULL,
	category_id INT NOT NULL,
	FOREIGN KEY (category_id) REFERENCES categories (category_id)
);

-- tablega ma'lumot yozish
INSERT INTO categories (category_name)
VALUES
	('Smart Phone'),
	('Laptop'),
	('Tablet');

INSERT INTO products (product_name, category_id)
VALUES
	('iPhone', 1),
	('Samsung Galaxy', 1),
	('HP Elite', 2),
	('Lenovo Thinkpad', 2),
	('iPad', 3),
	('Kindle Fire', 3);

-- NATURAL JOIN
SELECT * FROM products
NATURAL JOIN categories;
-- 
SELECT	* FROM products
INNER JOIN categories USING (category_id);