Re: Useful Oracle books - C.J. Date theory vs. practicality

• 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_at_optusnet.com.au
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