Thomas SMETS writes:
> <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>
>
> OK I'll start searching for it but haven't implemented yet
In the PostgreSQL distribution there's a directory contrib/isbn_issn that
defines a couple of data types that might help you.
--
Peter Eisentraut peter_e@gmx.net http://yi.org/peter-e/