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 !
You can only use the special NULL value to suppress the foreign key check on those rows that don't have a
parent. Then it'd be
CREATE TABLE categories ( id_category serial PRIMARY KEY, id_category_parent
integer,
FOREIGN KEY (id_category_parent) REFERENCES categories (id_category) ON DELETE
CASCADE );
Jan
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