The meaning of "relational"

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Nice try, but not quite there

I would strongly recommend C. J. Date's "Database in Depth" for anyone interested in a very clear explanation of relational theory.

Set theory is important of course but not, I think, as central as predicate logic; we are not just interested in representing and manipulating data but also in guaranteeing its logical integrity and this is central to the relational model (and to any true implementation of it).

You are right that there is a disturbing level of ignorance about the relational model at large but this is not by any means confined to the PC or mainframe worlds. We might witness the number of people who believe a relation, which is an n-dimensional mathematical structure, to be a "flat table". Given that I can describe the dimensions of a cube as a relation eg: {(5, 3, 4)} presumably these people also believe cubes to be flat.

I would also say that you could only sell a product like MySQL to people who are ignorant of relational theory. MySQL's commercial success is sadly indicative of how many these people there are. Think about some of Mikos's statements about constraints; now imagine a used car salesman dismissing brakes as "an enterprise feature". Not safe at any speed!

I would however say that all current SQL products violate relational principles sufficiently to not qualify as being relational.

Posted by: jorwell   Posted on: 06/06/06 You are currently: a Guest | Members login | Terms of Use

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