how to pass a null value to a foreign key field?

Question

I have 2 tables:

university:

university_id(p.k) | university_name

and user:

uid | name |          


        

Answer 1

I was using MySQL InnoDB and even allowing NULL in the FK column and using NULL as default I was getting an error. So I used the SET syntax:

INSERT INTO (table) SET value1=X...

And I just don't set the FK column.