Re: Useful Oracle books - C.J. Date theory vs. practicality
- From: Nuno Souto <dbvision@xxxxxxxxxxxxxxx>
- To: Oracle L <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 28 May 2004 22:32:35 +1000
-------- Original Message --------
Subject: Re: Useful Oracle books - C.J. Date theory vs. practicality
Dan Tow wrote:
troubles that relate to them. It is important to understand that null might
mean "We don't know this property of this entity." OR it might mean "This
NULL means NULL and preciously NOTHING else. You cannot EVER assign
a presumed meaning to something that means nothing.
single person, being a good example.) I'd personally like to see extensions to
SQL to handle these subtleties. The subtleties are there, however, whether we
The extensions are there: they are called default values.
And value constraints.
As soon as you append a value to the notion of NULL, it stopped
being a NULL and is now a special case. Which you should handle
using the value constraints.
The problem is that people CONTINUALLY refuse to believe that NULL
means exactly that: nothing. And NULL more!
--
Cheers
Nuno Souto
in sunny Sydney, Australia
dbvision@xxxxxxxxxxxxxxx
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