title: Zf2 NOT IN expression in Where clause
body: <p>I am trying to get a results from a table that is not already present on another table. 
  For this I am using a subQuery and a <strong>NOT IN</strong> expression in where clause. The normal sql that works looks like:</p>
  
  <pre><code>SELECT `products`.* FROM `products` WHERE `products`.`pro_id` **NOT IN** (
  SELECT `product_collection`.`pro_id` AS `pro_id` FROM `product_collection` WHERE `coll_id` = '6' ) AND products.pro_id IN (55,56,57,62)
  </code></pre>
  
  <p>I am using zf2 for the project. The problem is I dont know how to use <strong>NOT IN</strong> expression inside the where clause. We can use where->in() for the IN expression in Where clause. for eg.</p>
  
  <pre><code>//$productIds is an array
  //$collectionId is an id
  
  $subSelect = $this-&gt;getRawSql()-&gt;select('product_collection');
  $subSelect -&gt; columns(array('pro_id'));
  $subSelect -&gt; where(array('coll_id'=&gt;$collectionId));
  
  $select = $this-&gt;getRawSql()-&gt;select('products');
  $select -&gt; **where-&gt;in**('products.pro_id', $subSelect)
          -&gt; where-&gt;in('products.pro_id',$productIds);
  </code></pre>
  
  <p>but I have no idea how to use NOT IN expression. </p>