On 4/26/05, Jay Blanchard <[EMAIL PROTECTED]> wrote:
> [snip]
> The same is true for any other value... Now that the columns have a NOT
> NULL
> constraint the records that previously contained NULL now hold '0'.
>
> x y
> x 0
> x z
> x 0
>
> Now, how do you uniquely identify the 2nd and 4th rows?
> [/snip]
>
> The database would have thrown an error when you tried to create row 4.
No. NULL is not a value. It is a lack of value. Kind of a special
symbol, like infinity in mathematics. You cannot say that
infinity = infinity or infinity <> infinity. Same as you cannot
say that NULL = NULL or NULL <> NULL.
Regards,
Dawid
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