Question

I’m trying to build a navigation system using categories table with hierarchies. Normally, the table would be defined as follows:

id (int) - Primary key
name (varchar) - Name of the Category
parentid (int) - Parent ID of this Category referenced to same table (Self Join)

But the catch is that I require that a category can be child to multiple parent categories.. Just like a Has and Belongs to Many (HABTM) relation.

I know that if there are two tables, categories & items, we use a join table categories_items to list the HABTM relations. But here i’m not having two tables but only table but should somehow show HABTM relations to itself. Is this be possible using a single table? If yes, How? If not possible, what rules (table naming, fields) should I follow while creating the additional join table?

I’m trying to achieve this using CakePHP, If someone can provide CakePHP solution for this problem, that would be awesome. Even if that’s not possible, any solution about creating join table is appreciated. Thanks for your time.

— Edit —
My question seems to be a bit confusing, so I’m trying to restate what I’m looking for.
In traditional self referenced (self join) parent-child relations, each item can have only one parent. What I’m looking for is to simulate a HABTM relation i.e. multiple parents for each item.

Categories & Items – To define HABTM, we use categories_items join table.

If within Categories I need HABTM, what should I do?

Answer 1

Got it finally.

Naviitems Table:

CREATE TABLE IF NOT EXISTS `naviitems` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(50) NOT NULL,
  `linkurl` varchar(250) NOT NULL,
  PRIMARY KEY (`id`)
);

Self Join Table:

CREATE TABLE IF NOT EXISTS `naviitems_parents` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `naviitem_id` int(11) NOT NULL,
  `parent_id` int(11) NOT NULL,
  PRIMARY KEY (`id`)
);

Naviitems Model:

<?php
class Naviitem extends AppModel {

    var $name = 'Naviitem';

    //The Associations below have been created with all possible keys, those that are not needed can be removed
    var $hasAndBelongsToMany = array(
        'Parent' => array(
            'className' => 'Naviitem',
            'joinTable' => 'naviitems_parents',
            'foreignKey' => 'naviitem_id',
            'associationForeignKey' => 'parent_id',
            'unique' => true,
            'conditions' => '',
            'fields' => '',
            'order' => '',
            'limit' => '',
            'offset' => '',
            'finderQuery' => '',
            'deleteQuery' => '',
            'insertQuery' => ''
        )
    );
}
?>

I’ve generated the Controller and Views using Cake Bake shell. It’s working fine now. Thanks for all the ideas you’ve contributed, they’ve helped me a lot.