ok im dumb - but this is the novice list -
references category(category_id)
worked after Id done everything correct
mwaples(at)optusnet(dot)com(dot)au wrote:
>
> I have a table category with columns -
> category_id , main_id
>
> I would like to check that the main_id value exists in category_id in
> any row of the table category.
>
> Is it possible to have a foreign key referring to the current table ?
> Or should I be using a trigger to do it ?
>
> I'm thinking I have to use a trigger to do it - but want to make sure.