Adding a column as a foreign key gives ERROR column referenced in foreign key constraint does not exist

Question

I have the following set up,

CREATE TABLE auth_user ( id int PRIMARY KEY );
CREATE TABLE links_chatpicmessage ();

I\'m trying to add a

Answer 1

****foreign key reference for existing column****

ALTER TABLE table_name ADD CONSTRAINT fkey_name FOREIGN KEY (id) REFERENCES ref_table(id)