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

On Sat, 19 Nov 2005 23:19:58 +0000, Bernard Peek wrote:

>In message <fn5sn19kcr7og6p8hjnodb7j67umo6tbu9_at_4ax.com>, Gene Wirchenko
><genew_at_ucantrade.com.NOTHERE> writes
>
>> Does an object exist? If it does, we get the answer yes. If it
>>does not, we get the answer no. No NULL is needed.
>
>Does my dog exist?

Hi Bernard,

Almost there. Almost.

Does my dig exist? is a yes/no question. The answer to that is a boolean value. And booleans are not defined as a data type in SQL. There's a reason for that. All SQL data types can also accomodate a Null, but a boolean can't. All yes/no questions can allways be answered. Not with "yes" (true), "no" (false), or "no answer" (Null), but with "yes", "no", or "don't know" (unknown).

A better example would be:

What's the age (in whole years) of my dog?

Best, Hugo

-- 

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