Re: UNIQUE and NULL in SQL
From: David Cressey <david_at_dcressey.com>
Date: Mon, 31 Dec 2001 13:11:23 GMT
Message-ID: <%tZX7.5$Nq6.437_at_petpeeve.ziplink.net>
Date: Mon, 31 Dec 2001 13:11:23 GMT
Message-ID: <%tZX7.5$Nq6.437_at_petpeeve.ziplink.net>
> What would be the rationale behind UNIQUE if it was any different to
> this? That is, what makes the first NULL different to your second
> NULL?
>
NULL is not equal to NULL. NULL is also not unequal to NULL.
If the test is NULL = NULL, the result is NULL. If the test is NULL <> NULL, the result is NULL.
--
Regards,
David Cressey
www.dcressey.com
Received on Mon Dec 31 2001 - 14:11:23 CET