SET @fila1 = 0;
SET @fila2 = 0;
SET @faena = 1559;
SET @patente = "HYGD-72";
UPDATE tbl_disp_cam_detalle tdcd
inner join
(SELECT
	 v2.id,
    v1.fecha as fechaInicial, v2.fecha as fechaFinal, v2.horometro,
    v2.horometro - v1.horometro as diferencia,
    datediff(v2.fecha, v1.fecha) as cantidadDiasMedida
FROM
    (SELECT dcd.id, (@fila1:=@fila1 + 1) AS num,
    STR_TO_DATE(CONCAT(dcd.ano,'-',dcd.mes,'-',dcd.dia), '%Y-%m-%d') as fecha,
    dcd.horometro as horometro
    FROM tbl_disp_cam_detalle dcd
    WHERE  dcd.cod_faena =  @faena AND dcd.patente = @patente
    order by dcd.ano, dcd.mes, dcd.dia ASC) v1,

    (SELECT dcd.id, (@fila2:=@fila2 + 1) AS num,
    STR_TO_DATE(CONCAT(dcd.ano,'-',dcd.mes,'-',dcd.dia), '%Y-%m-%d') as fecha,
    dcd.horometro as horometro
    FROM tbl_disp_cam_detalle dcd
    WHERE  dcd.cod_faena = @faena AND dcd.patente = @patente
    order by dcd.ano, dcd.mes, dcd.dia ASC) v2
WHERE v1.num + 1 = v2.num) vista
ON tdcd.id = vista.id
SET dif_med_ant = vista.diferencia WHERE tdcd.id = vista.id