On Friday 25 June 2004 09:37, Rosser Schwarz wrote:
> On Fri, 25 Jun 2004 08:16:47 +0400, sad <sad(at)bankir(dot)ru> wrote:
> > > Very simply, a boolean may have to values: true or false. It's also
> > > possible that it's not been set to anything (NULL).
> >
> > really ?
> > what about (13 < NULL)::BOOL
>
> Per the semantics of NULL, 13 is neither greater than nor less than
> NULL. NULL is the *unknown* value; it's impossible to meaningfully
> compare it to anything else. Try (NULL = NULL)::boolean. It's NULL,
> also.
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