Stephan Szabo <sszabo@megazone.bigpanda.com> wrote:
>
>
> On Tue, 27 Jul 2004, BRINER Cedric wrote:
>
> > hi,
> >
> > Imagine that I have the following table where ts_sent is a timestamp(0)
> >
> > select * from notification;
> > to_used | ts_sent | from
> > ---------------------+-------------------------+---------
> > amanda@obs.unige.ch | 2004-07-21 14:19:43+02 | amanda
> > amanda@obs.unige.ch | | postgres
> >
> > and so, how do I do to fetch the second line by asking :
> > catch me the line where ts_sent doesn't have a value !
> >
> > I've try:
> > select * from notification where ts_sent = null ;
>
> Use ts_sent IS NULL, not ts_sent = null.
>
> Pretty much, <anything> = null returns null.
To expand on this... This is because NULL is nothing. Not zero, but
*nothing*. Being nothing, it cannot "equal" anything. Not even
itself. But a space can *contain* nothing. And it can contain "not
nothing."
Jim
