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

The CONSTRAINT clause is optional. I suggest ommiting it and always letting PostgreSQL autoname the constraint, without naming it you'll get a logical name

"links_chatpicmessage_sender_fkey" FOREIGN KEY (sender) REFERENCES auth_user(id)

That's what you'll likely want to know if an INSERT or UPDATE fails due to a constraint violation.

Syntax to add a foreign key

All of these are somewhat documented on ALTER TABLE

To a new column

ALTER TABLE links_chatpicmessage 
  ADD COLUMN sender int,
  ADD [CONSTRAINT foo] FOREIGN KEY (sender) REFERENCES auth_user(id);

This is compound and transactional. You can issue two ALTER statements on the same table by separating the two statements with a ,.

To a preexisting column

-- assumes someone has already added the column or that it already exists
ALTER TABLE links_chatpicmessage
  ADD COLUMN sender int;

ALTER TABLE links_chatpicmessage
  ADD [CONSTRAINT foo] FOREIGN KEY (sender) REFERENCES auth_user(id);