CREATE TABLE items (
  id integer AUTO_INCREMENT,
  name varchar(255) NOT NULL,
  price int unsigned NOT NULL,
  PRIMARY KEY (id)
)

CREATE TABLE companies (
  id integer AUTO_INCREMENT,
  name varchar(255) NOT NULL,
  address varchar(255) NOT NULL,
  PRIMARY KEY (id)
)

CREATE TABLE orders (
  id integer AUTO_INCREMENT,
  date date NOT NULL,
  company_id integer NOT NULL,

  PRIMARY KEY (id),
  INDEX (company_id),
  FOREIGN KEY(company_id)
    REFERENCES companies(id)
)

CREATE TABLE order_details (
  order_id integer NOT NULL,
  item_id integer NOT NULL,
  number integer unsigned NOT NULL,

  PRIMARY KEY (order_id, item_id),

  FOREIGN KEY(order_id)
    REFERENCES orders(id)
    ON DELETE CASCADE,

  FOREIGN KEY(item_id)
    REFERENCES items(id)
)