Hugo Kornelis wrote:

> So short answer - don't use a default to signify missing data, use NULL.
> And make sure that you understand three-valued logic and other quirks of
> the behaviour of NULL.

Can you suggest any good references on this topic??
The ones I know of are based on Access, and I'm sure SS2005 is quite
different!!!

> really the most appropriate for a "missing value" marker. But I don't
> think that you'll find anyone who would argue that '123-45-6789' will
> ever behave more appropriate for "missing value" than NULL does.

Wouldn't using a default value at least avoid the issues of using NULL
per se??

Thank you, Tom