Calculate alphabetic sequence

if object_id(N'fn_Calc_AlfaSeq', N'FN') is not null
    drop function dbo.fn_Calc_AlfaSeq
go

CREATE FUNCTION dbo.fn_Calc_AlfaSeq(@in_cod VARCHAR(100))
	RETURNS VARCHAR(100)
AS
BEGIN

	declare @ret_cod	varchar(100),
			@l1			char(1), 
			@l2			char(1), 
			@l3			char(1),
			@i			int,
			@p			int,
			@ascii		int,
			@stop		bit

	declare @array table (id int, valor char(1))


	set @i = 1
	while @i<=len(@in_cod)
	begin
		insert into @array (id,valor) select @i, substring(@in_cod,@i,1)
		set @i = @i+1
	end

	set @i = (select max(id) from @array)

	set @stop = 0
	while @i>=1 and @stop=0
	begin
		set @ascii = (select ascii(valor) from @array where id=@i)
		if @ascii+1<91
		begin
			set @p=@i
			set @stop = 1
		end

		set @i=@i-1
	end

	set @ret_cod = ''
	select @ret_cod = @ret_cod + case when id<@p then valor else case when id=@p then char(ascii(valor)+1) else 'A' end end from @array order by id

	return @ret_cod
		
END

go
GRANT  EXECUTE  ON dbo.fn_Calc_AlfaSeq TO [public]