On Sat, 9 Jun 2001, Postgresql wrote:
> Hi,
>
> I have a table of categories (it's pseudo-sql...) :
>
> CATEGORIES
> (
> id_category PRIMARY KEY,
> id_category_parent (FOREIGN KEY ? CONSTRAINT ??) ,
> cat_text
> )
>
> There is recursivity : id_category_parent is -1 (= no parent cat) or the
> id_category of a category in this table.
> What is the SQL statements to create such a table so that when you delete a
> category, all sub-categories
> are automatically deleted ?
> I've tried many things like CONSTRAINT... but the query fails !
If you want to use foreign keys, using -1 for no cat is going to mean
you're going to need a -1 category. You're probably better off using
NULL for that.
you probably want something like:
id_category_parent REFERENCES categories ON DELETE CASCADE
[you may want to add ON UPDATE CASCADE]