title: Get only first element from database
body: <p>I want to show bought "products names" in prestashop orders page.
  For prestashop 1.6 i already have a code that works, but using the same code on prestashop 1.7 give me duplicate orders ...</p>
  
  <pre><code>public function getProductsName($id_order, $tr)
  {
      $products=Db::getInstance()-&gt;executeS(
          'SELECT product_name FROM '._DB_PREFIX_.'order_detail
          WHERE id_order='.(int)$id_order);
      $str='';
      foreach($products as $val) {
          $str.=substr($val['product_name'],0,35).'| ';
          }
      $str=trim($str,'|');
      return $str;
  }
  </code></pre>