title: How to multiply with sum in Laravel
body: <p>I would like to multiply sales.price with merchants.commission with Laravel Query Builder. Currently my query looks like this, but I unfortunately do not know what do proceed. Help is kindly appreciated.</p>
  
  <pre><code>DB::table('sales')
  -&gt;leftJoin('merchants', 'sales.merchant', '=', 'merchant.id')
  -&gt;sum("");
  </code></pre>