UPDATE mySock s1
LEFT JOIN mySock s2
 ON s1.parentId = s2.id
SET
   s1.status = 1
   s1.mylevel = (s2.mylevel + 1),
   s1.parentString = CONCAT(s2.parentString, ':' CONCT(s1.id as char))
WHERE
    s1.zz = 0;

public function updateParentNew($idParent)
{
    return $this->createQueryBuilder('s1')
        ->update('MyBundle:Stock', 's1')
        ->leftJoin(''MyBundle:Stock', 's2', 'WITH', 's2.id = s1.parentId')
        ->set('s1.zz', 1)
        ->set('s1.leveltask', 's2.leveltask + 1')
        ->set('s1.parentString', '?par2_string')
        ->where('s1.zz = 0')
        ->andWhere('s1.parentId = ?par1')
        ->setParameter('par1', $idParent)
        ->setParameter('par2_string', s2.parentString + ':' + (string)s1.id)
        ->getQuery()->getSingleScalarResult();
}