David Portas wrote:
>>yes, in theory, the SQL Server approach is more 'pure'
>
>
> Not really. The SQL standard consistently defines all the nullable
> constraints (CHECK, UNIQUE, FOREIGN KEY) in the negative. In other words,
> the constraint doesn't permit violations (logical FALSE) but nor does it
> require that the constraint be satisfied (logical TRUE). The UNKNOWN case is
> not considered a violation of a constraint, which is why NULLs are
> permitted. Unfortunately Microsoft disagrees ;-)
Actually that isn't entirely true. SQL Server, in order to claim ANSI
compliance has a parameter that allows it to work as does Oracle. It
just isn't the default. And since most SQL Server types can't or don't
read manuals I can't think of a single instance where I've seen it set
for ANSI compliance.
--
Daniel A. Morgan
University of Washington
damorgan_at_x.washington.edu
(replace 'x' with 'u' to respond)
Received on Fri Oct 22 2004 - 00:07:35 CDT
