# Re: NULLs: theoretical problems?

From: Jan Hidders <hidders_at_gmail.com>

Date: Mon, 20 Aug 2007 21:39:58 -0000

Message-ID: <1187645998.798282.58960_at_g4g2000hsf.googlegroups.com>

Date: Mon, 20 Aug 2007 21:39:58 -0000

Message-ID: <1187645998.798282.58960_at_g4g2000hsf.googlegroups.com>

On 20 aug, 17:14, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:

> Jan Hidders <hidd..._at_gmail.com> wrote in news:1187599195.269472.153110

*> _at_a39g2000hsc.googlegroups.com:
**>
**> > On 20 aug, 01:48, "V.J. Kumar" <vjkm..._at_gmail.com> wrote:
**> >> I wonder what the truth tables for 'AND' and 'OR' would look like with
**> >> the DEF operator. Could you show those tables ?
**>
**> > They would be the usual table you already gave:
**>
**> >> x y AND
**> >> -------
**> >> defined
**> >> 0 0 0
**> >> 1 0 0
**> >> 0 1 0
**> >> 1 1 1
**>
**> What is 'x AND y' equal to if x is '1' and y is not defined ?
*

The database would not allow you to write that. If y is nullable then it forces you to write "DEF y : x AND y".

- Jan Hidders