Re: cascading delete - recursivity

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]