Something

SELECT DISTINCT (nombrenivel3), idNivel3, idnivel1, idnivel2
           FROM comnet.jerarquiaestadisticas
          WHERE idempresa = '1' AND idnivel1 LIKE '__' AND idnivel2 LIKE '_'
		  group by nombrenivel3, idnivel3, idnivel1, idnivel2 having count (nombrenivel3) =1
       ORDER BY nombrenivel3