|Subject||RE: [firebird-support] Why NULL <> NULL ?|
> Alan McDonald wrote:ahhh, we need a consistent view on our data - you can't have a system which
> >>Often used example:
> >>I don't know how much money you've got in your wallet, so the value is
> >>NULL (unknown).
> >>You don't know how much money I've got in my wallet, so it's NULL, too.
> > I've never thought of this as a good example.
> > I have money in my wallet - it could be nothing or it could be
> $5 or $10 etc
> > In the DB, if the field state is NULL - it NEVER has an unknown
> value in it
> > of 5 or 10 - it has no value it's state is NULL. if it has 5 or 10 in it
> > then it is NOT NULL.
> But the key here is that NULL means unknown (to others than the wallet
> owner in the above example). So, to the wallet owner, the amount of
> money in his/her wallet is NOT NULL (unless he/she hasn't counted it for
> a while...), but to the rest of the world, it's NULL.
> Kjell Rilbe
reports NULL to some people and NOT NULL to others based on who is asking.