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

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. Its
value is an empty string (whatever "it" is). Different to having a
value of zero. Different to anything with a value. Now, as I read up on
SQL, I find that null is supposed to mean "unknown". I can't easily
accept that. 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? I can't
imagine having to write code where the "if a=b then result=true else
result=false" construct won't work - according to what I'm reading, if
either a or b is null then I should be setting result to unknown
instead. Just can't get my head 'round that. Shouldn't things be a lot
simpler? If something has an unknown value then at least we know
whether it's null (as in an empty string) or not. To me, "unknown" can
be compared with an empty string to see if it's null or not. Sorry -
head is spinning.

Mike.

.

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