cascading delete - recursivity - Mailing list pgsql-sql

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 !


Thanks !