create procedure modul_10 (@@number varchar(15))
as
begin
	/*
	**procedure to calculate modulus-10 checkdigit
	**procedure written 19980831 by andreas birgerson
	**last revision on  19980831 by andreas birgerson
	*/
	set nocount on
	
	declare @@max smallint
	declare @@counter smallint
	declare @@weight varchar(24)
	declare @@rest smallint
	declare @@value smallint
	
	select @@weight='121212121212121212121212'
	select @@max=datalength(@@number)
	select @@weight=right(@@weight,@@max)
	
	if not @@max between 2 and 15 begin
	raiserror('Modul-10 invalid argument length',2,-1) with seterror
	return
	end
	
	create table #f (chkdigit smallint null)
	select @@counter=@@max+1
	
	loop:
	select @@counter=@@counter-1
	select @@value=
	(ascii(substring(@@weight,@@counter,1))-48)*
	(ascii(substring(@@number,@@counter,1))
	-48)
	
	insert #f values
	(case
	when (@@value<10) then @@value
	when  (@@value>9) then @@value-10
	end)
	
	insert #f values
	(case
	when  (@@value<10) then null
	when  (@@value>9) then 1
	end)
	
	if @@counter >1 goto loop
	
	
	select @@rest=sum(chkdigit)%10 from #f
	
	select "Checkdigit"=case @@rest
	when 0 then 0
	else 10-@@rest
	end
	
	
	drop table #f
	set nocount off
end
	
	
go