Re: So what's null then if it's not nothing?
Date: Wed, 30 Nov 2005 22:48:43 +0100
On 29 Nov 2005 07:11:29 -0800, vc wrote:
The 3vl unknown isn't mapped to anything.
ANSI standard says:
- For SELECT: return rows if the condition in the WHERE clause evaluates to true; omit rows if it evaluates to either false or unknown. - For CONSTRAINT: accept rows if the constraint's condition evaluates to true or unknown; reject rows if it evaluates to false.
No mappping involved.
>, therefore, null is
>*not* a duplicate.
You can't say that null is not a duplicate - it is unknown if it's a duplicate or not.
-- (Remove _NO_ and _SPAM_ to get my e-mail address)Received on Wed Nov 30 2005 - 22:48:43 CET