unComplicate:

create table #tmp (x nvarchar(max))

declare @s-2 nvarchar(max) = 'a,1,2,x,3,4,z'

declare @aux nvarchar(max)

while charindex(',',@s) > 0

begin

set @aux = substring(@s,0,charindex(',',@s))

SET @s-2 = LTRIM(STUFF(@s,1,len(@aux)+1,''))

insert into #tmp select @aux

end

insert into #tmp select @s-2

select x from #tmp

drop table #tmp