title: Error when get value in from node father?
body: <p>I have a sample data:</p>
  
  <pre><code>product(id, parent_id, name)
          1 |  0  | Windows
          2 |  1  | XP
          3 |  1  | 7
  manufacturer(id, parent_id, name)
          1 |  0  | Westwood Studios
          2 |  1  | Red Alert 1
          3 |  1  | Red Alert 2
  product_manufacturer(product_id, manufacturer_id)
          2 |  2  
          3 |  2
          3 |  3
  </code></pre>
  
  <p>And mysql: </p>
  
  <pre><code>SELECT prod.name
  FROM `manufacturer` AS child
  INNER JOIN `manufacturer` AS parent ON parent.id=child.parent_id 
  INNER JOIN `product_manufacturer` AS pr_ma ON pr_ma.manufacturer_id=child.manufacturer_id
  INNER JOIN `product` AS prod ON pr_ma.product_id=prod.product_id 
  WHERE parent.id=1
  GROUP BY prod.id
  </code></pre>
  
  <p>When <code>parent.id=1 (manufacturer=Westwood Studios)</code> is result is <code>XP, 7</code></p>
  
  <p>How to fix when <code>parent.id=1</code> is result is <code>Windows</code></p>