Re: So what's null then if it's not nothing?
Date: 17 Nov 2005 14:41:19 -0800
Message-ID: <1132267279.450143.53040_at_g47g2000cwa.googlegroups.com>
Alfredo Novoa wrote:
> 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.
>
> A clear contradiction!
No! (oops - there's another one)
> 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.
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? It's whatever you stored to represent "unknown".
> > Its
> > value is an empty string (whatever "it" is).
>
> An empty string is a string like any other.
>
> >Does SQL's definition of null (unknown) include the null
> > I'm familiar with (no value)? That doesn't make sense. If we know
> > something has no value then its not an unknown value is it?
>
> Indeed, SQL nulls don't make sense.
At last - something we actually agree on. Cheers!
Not if something that doesn't exist = an empty string = null.
>
> Regards
> Alfredo
Received on Thu Nov 17 2005 - 23:41:19 CET