Thomas SMETS wrote:
>
> <snip>
> ISBN's have a checkdigit; it would be sensible to provide a
> function to be used in a CHECK constraint to ensure that the
> ISBN is valid.
> </snip>
Here's a URL with more
information:http://www.isbn.spk-berlin.de/html/userman/usm4.htm.
I've written a similar algorithm in C to create and verify checksums for
eight digit codes. The final code is then 9 digits. I did this to help
create codes that are the same length as a social security number. If
you'd like a copy, let me know.
-Ron-