title: Laravel Query Builder Update with Increment
body: <p>Hi I need to fix my query where I will need to update my product quantity with just incrementing it, here is my code with sample.</p>
  
  <pre><code>    DB::table('product_warehouse')
      -&gt;where('product_id', $product_id)
      -&gt;where('warehouse_id', $warehouse_id)
      -&gt;update(['product_qty' =&gt; $old_qty+$product_qty]);
  </code></pre>