title: Rails active record find where nil
body: <p>I have a cost attribute for my product model and its type is <code>float</code> and everything works well.
  When creating a new product, a user can enter 0 or leave blank for a free product or enter the cost when its a paid product and so far that also works well</p>
  
  <p>Now i am trying to scope free items, but since float is returning <code>NIL</code> for empty fields and i cannot return nil fields.</p>
  
  <p>i tried</p>
  
  <p><code>scope :free, where("cost IS NULL or cost &lt; ?", 1 )</code></p>
  
  <p>and it doesn't return fields that are blank (NIL) but fields with 0 only but i want to return both blank (NIL) fields and 0 fields. I know float fields in rails 3 return <code>nil</code> instead of <code>null</code></p>