Re: When is a record NULL?

On Sun, Jul 26, 2009 at 12:49:32PM -0500, Kevin Grittner wrote:
> Codd, E.F. (1990). The Relational Model for Database Management
> (Version 2 ed.). Addison Wesley Publishing Company.
> ISBN 0-201-14192-2.

Looks as though I've got some reading to do then--somewhat annoying that
only second hand copies available from the US, but never mind!

> I believe that he puts forward a list of about 200 things he feels
> should be true of a database in order for him to consider it a
> relational database. Since he was first and foremost a mathematician,
> and was something of a perfectionist, I don't think some of these are
> achievable (at least in the foreseeable future) without tanking
> performance, but it makes for an interesting read. I find most of it
> to be on target, and it gives a unique chance to see things from the
> perspective of the inventor of relational model for database
> management.

Yup, I've heard lots and read a few smaller articles but don't think
I've got around to any of his books.

> I don't, of course, agree with him on everything. If you think that
> the SQL standard date handling is weird, wait until you see how a
> perfectionist mathematician attempts to deal with it. :-) Also, the
> requirement that, to be considered a relational database, it must be
> impossible to write two queries which can be shown to be logically
> equivalent but which optimize to different access plans to be, well, a
> bit "ivory tower."

Sounds as though he's using a different definition than what I would
use, but I'm sure I'll find out.

--
Sam http://samason.me.uk/