create or replace function f_pruefz_ean13(pin_ean number) return number is

/******************************************************************************
 *Heiko Hommes
 *10.11.2010
 *Prüfziffernberechnung ean13
 *Übergabe 12 stellige eannr
 *Rückgabe Prüfziffert
 ******************************************************************************/
 
 va_ean varchar2(255) := '';
 vn_prfz number := 0;
 
 begin
               
      va_ean := to_char(pin_ean);
      vn_prfz := to_number(substr(va_ean,1,1)) * 1 + to_number(substr(va_ean,2,1)) * 3 +
                to_number(substr(va_ean,3,1)) * 1 + to_number(substr(va_ean,4,1)) * 3 +
                to_number(substr(va_ean,5,1)) * 1 + to_number(substr(va_ean,6,1)) * 3 +
                to_number(substr(va_ean,7,1)) * 1 + to_number(substr(va_ean,8,1)) * 3 +
                to_number(substr(va_ean,9,1)) * 1 + to_number(substr(va_ean,10,1)) * 3 +
                to_number(substr(va_ean,11,1)) * 1 + to_number(substr(va_ean,12,1)) * 3
                ;
      vn_prfz := (to_number(substr(to_char(vn_prfz),1, length(to_char(vn_prfz)) -2) || to_char(to_number(substr(to_char(vn_prfz),length(to_char(vn_prfz)) -1 ,1) + 1) * 10))) - vn_prfz ;
      return  vn_prfz;
      
    
 exception when others then
   return null;    

end f_pruefz_ean13;