create table #scott (
    pk int identity(1,1) not null primary key,
    num1 numeric(25,20),
    num2 numeric(25,20),
    num3 numeric(25,20),
    num4 numeric(25,20),
    num5 numeric(25,20) )
go

insert into #scott (num1,num2,num3,num4,num5)
select
    rand(cast(newid() as binary(4))) * 1000,
    rand(cast(newid() as binary(4))) * 1000,
    rand(cast(newid() as binary(4))) * 1000,
    rand(cast(newid() as binary(4))) * 1000,
    rand(cast(newid() as binary(4))) * 1000
from
    #numbers -- (10000 rows)
go

select
    pk,
    case when num1 >= num2 and
              num1 >= num3 and
              num1 >= num4 and
              num1 >= num5 then num1
         when num2 >= num1 and
              num2 >= num3 and
              num2 >= num4 and
              num2 >= num5 then num2
         when num3 >= num1 and
              num3 >= num2 and
              num3 >= num4 and
              num3 >= num5 then num3
         when num4 >= num1 and
              num4 >= num2 and
              num4 >= num3 and
              num4 >= num5 then num4
         else num5
    end as maxnum
from
    #scott
order by
    pk

select
    s.d.pk,
    max(d.num) as maxnum
from
    #scott
    inner join (
    select pk,num1 as num from #scott
    union all
    select pk,num2 as num from #scott
    union all
    select pk,num3 as num from #scott
    union all
    select pk,num4 as num from #scott
    union all
    select pk,num5 as num from #scott) d
    on s.pk = d.pk
group by s.d.pk
order by
    s.d.pk