>BUT, this being a limitation of the current UPDATE - SQL, it sure would be helpful to get an error when one specifies (or tries) something beyond its capabilities.

But it's not an error. It simply uses the values from the current record in the other tables. For code like that to cause an error, you'd have to be prohibited from referencing a field of a table not in the command. I don't know that we'd want that limitation.

>Maybe you can note this in your next Hacker's publication.

Yeah, I see that we don't say it explicitly. Looking at that entry, I also note that you probably could do what's wanted here with a subquery in the WHERE clause.

Tamar