title: Rails raw SQL example
body: <p>How can I convert this code to raw sql and use in rails? Because When I deploy this code in heroku,there is a request timeout error.I think this will be faster if I use raw sql.</p>
  
  <pre><code>@payments = PaymentDetail.joins(:project).order('payment_details.created_at desc')
  @payment_errors = PaymentError.joins(:project).order('payment_errors.created_at desc')
  
  @all_payments = (@payments + @payment_errors)
  </code></pre>