Include the FOREIGN KEY keywords in the
ADD clause to add a foreign key to a table definition.
Include a FOREIGN KEY clause in your
CREATE TABLE statement to define a foreign key on a dependent table. In addition to specifying a list of columns for the key, you can define a name for the key.
You cannot create a self-referencing foreign key with the CREATE TABLE statement. Use an
ALTER TABLE statement to create a foreign key that references the primary key in the same table.