SQL - Cómo obtener la primera y la utlimo registros

select FirstName as 'Nombre',LastName as 'Apellido',description as 'entrada',

CONVERT(VARCHAR(10),TimeStamp_Server,103) AS Fecha,

		RIGHT(TimeStamp_Server, 7) AS Hora  from Message

where Description = 'Torniquete Entrada'

order by fecha

-- Datos en tabla de entrada

--id  group   val   start   end

--1   10      36    465     89

--2   10      35    55      11

--3   10      34    20      456

--4   20      38   1140     1177

--5   20      22    566     788

--6   20      1235  789     4796

--7   20      7894  741     1067

-- Resultado deseado

--id  group   val   start   end

-- 1   10      36    465     89

-- 3   10      34    20      456

-- 4   20      38   1140     1177

-- 7   20      7894  741     1067

drop table #test

create table #test ([id] int, [group] int, [val] int, [start] int, [end] int)

insert into #test values(

1   ,10      ,36    ,465     ,89),

(2   ,10      ,35    ,55      ,11),

(3   ,10      ,34    ,20      ,456),

(4   ,20      ,38   ,1140     ,1177),

(5   ,20      ,22   ,566     ,788),

(6   ,20      ,1235  ,789     ,4796),

(7   ,20      ,7894  ,741     ,1067)

WITH Cte AS(

    SELECT *,

        RnAsc = ROW_NUMBER() OVER(PARTITION BY [group] ORDER BY val),

        RnDesc = ROW_NUMBER() OVER(PARTITION BY [group] ORDER BY val DESC)

    FROM #test

)

SELECT

    id, [group], val, start, [end]

FROM Cte

WHERE

    RnAsc = 1 OR RnDesc = 1

ORDER BY [group], val