Re: So what's null then if it's not nothing?

>> michael_at_preece.net wrote:
>>> I've been accustomed to thinking of things either having a value or
>>> not. If something has no value then, to me, its value is null.
>>
> Alfredo Novoa wrote:
>> A clear contradiction!
>
michael_at_preece.net wrote:
> No! (oops - there's another one)
>
> Alfredo Novoa wrote:
>> If something has no value then it has no value.
>
> Yes - and it is therefore equal to null. Null is no value. Null is an
> empty string. If something doesn't exist its value is not unknown - it
> is null - it is an empty string - it has no value.

These axioms are only true in Pick -- and not always then (see my 5NF post.)

michael_at_preece.net wrote:
> I didn't have to respond to this. If I hadn't you would never had
> known what I thought about your post. My response would not exist.
> What you would be reading here would have no value. It would have
> been an empty string. It would also have been unknown. If you wanted
> to you could record this discussion in a database - and record my
> possible response as unknown - you could record it as a null. To be
> fair though you ought to also record everyone else on the planet's
> response as null - or unknown.
>
> You will say that at the logical level something can exist - in that
> it is part of a set - and yet have an unknown value. You would,
> presumably - also say that it does not necessarily have a value equal
> to empty string, because it's unknown. In order to record that "fact"
> you (or the SQl engine) have/has to store some code at the physical
> level to say it's not an empty string - it's null. It's not though is
> it?

Unfortunately, SQL uses the word "null" for this. Hence your confusion, I believe. Would you feel the same way if they called it "unknown?"

> It's whatever you stored to represent "unknown".
Exactly!

[some snippage]

-- 
frosty