psql -U devuser acme

CREATE TABLE articles(id SERIAL PRIMARY KEY, title VARCHAR(255), body TEXT);

\dt

INSERT INTO articles(title, body) VALUES('Article One', 'This is the body for article 1');

SELECT * FROM articles;

INSERT INTO articles(title, body) VALUES('Article Two', 'This is the body for article 2');

INSERT INTO articles(title, body) VALUES('Article Three', 'This is the body for article 3');

SELECT * FROM articles;

CREATE TABLE categories(id SERIAL PRIMARY KEY, name VARCHAR(255));

\dt

INSERT INTO categories(name) VALUES('Business'), ('Technology'), ('Style');

SELECT * FROM categories;

ALTER TABLE articles ADD COLUMN category_id INT;

UPDATE articles SET category_id = 1 WHERE id = 1;

UPDATE articles SET category_id = 1 WHERE id = 2;

UPDATE articles SET category_id = 2 WHERE id = 3;

SELECT * FROM articles;

ALTER TABLE articles ADD CONSTRAINT catfk FOREIGN KEY(category_id) REFERENCES categories(id);

DELETE FROM articles WHERE id = 3;

SELECT * FROM articles;