SimpleLoop.sql

declare @Result Table(StationName VarChar(50))
declare @Position VarChar(50) = 'A'

while(@Position is not null)
BEGIN
	insert into @Result values(@Position)
	declare @Override varchar(50) = (select top 1 StationToName from StationRoutingOverride where StationFromName = @position)
	declare @Failover varchar(50) =
	(select top 1 S2.StationName from Stations S1
	join Stations S2 on S2.StationPhysicalOrder = S1.StationPhysicalOrder+1
	where S1.StationName = @Position)
	set @Position = coalesce(@Override,@Failover)
END
select * from @Result