Re: In an RDBMS, what does "Data" mean?

"Paul" <paul_at_test.com> wrote in message
news:Zqixc.12382$NK4.1717725_at_stones.force9.net...
> Here's a thought: consider a database with the constraints "Age < 65"
> and "Age < 60". Should there be something to say this isn't normalised
> in some sense? I know that normalization and eliminating redundancy are
> different things but maybe there should be some kind of "constraint
> normalization"?

Implication is one part of it; since [Age<60] implies [Age<65], the latter is unnecessary. The relational model, by relying on such, make more optimizations possible than some of the ad hocisms of SQL and the like - and they certainly get much more complex than this example...

An interesting related point is the overlap between types and constraints. In the above, isn't it really an example of an Age type, with values [0, 1, ..., 60]? (assuming integers here)

• erk