Re: 3vl 2vl and NULL

From: David Cressey <dcressey_at_verizon.net>
Date: Mon, 12 Dec 2005 04:16:22 GMT
Message-ID: <qQ6nf.1674$Bj4.25@trndny01>

"Hugo Kornelis" <hugo_at_pe_NO_rFact.in_SPAM_fo> wrote in message news:aaepp1l4g1h3ud0imb120471k08g9rdaf0_at_4ax.com...

> All true. The DB engine can conclude the datatype of the NULL from the
> datatype of the column that holds the NULL. Or when used as a literal in
> a query (though I fail to see why anyone would do that), it can either
> choose a datatype from the context or choose a default datatype and use
> implicit conversion rules to get at the destination datatype.

I would change the wording slightly.

The DB engine can conclude the datatype a value would have if it were in the place currently occupied by the NULL.

NULL doesn't have a datatype. The place marked by a NULL can contain a value drawn from a domain. Any value in that lpace has a datatype. NULL doesn't. Received on Sun Dec 11 2005 - 22:16:22 CST