Re: Distributed key constraints

Roy Hann wrote:
> Is there any commercially available dialect of SQL which implements
> declarative distributed key constraints? (I'm betting not.) Failing
that,
> has anyone ever proposed syntax them?
>
> Roy

If by distributed you mean 'in more than one database', then I'm not answering your question, but if by distributed you mean 'in more than one table' then, yes, there is one system that would allow you to enforce such a constraint without resorting to stored procedures or client-side enforcement. But it's not SQL. Dataphor by Alphora supports transition constraints which can be used to write an expression for each table involved in the constraint and enforce a key that spanned multiple tables.

If this isn't what you meant, sorry. Darwen has used the term distributed key to describe a key constraint involving multiple relation variables, but I prefer the term generalized key because it avoids precisely the confusion we may be seeing here. I believe he did propose some syntax for them in the paper in which he introduced the term.

Hope this helps,
Bryn Received on Thu Apr 28 2005 - 08:55:41 CEST