doctrine native sql

<?php
 
class ItemGroupController extends Controller
{
 
    /**
     * Lists all ItemGroup entities.
     *
     * @Route("/", name="api_itemgroup")
     * @Method("GET")
     * @Template()
     */
    public function indexAction()
    {
        /**
         * @var \Doctrine\ORM\EntityManager
         */
        $em = $this->getDoctrine()->getManager();
 
        $sql = <<<SQL
select
	itemgroup.`id` as `id`,
	itemgroup.`name` as `name`,
    itemgroup.`type` as `type`,
    concat('[', group_concat(groupmapper.item_id separator ','), ']') as `items`
from item_group as itemgroup
	left join item_group_mapper as groupmapper on itemgroup.id = groupmapper.group_id
group by itemgroup.id
SQL;
 
        $q = $em->getConnection()->executeQuery($sql);
 
        $groups = $q->fetchAll();
 
        return new JsonResponse(array(
            'entities' => $groups,
        ));
    }
}