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Re: Can FK be nullable/optional by design?

From: Tobes \(Breath\) <tobin_dont_spam_me_at_breathemail.net>
Date: Wed, 17 Dec 2003 17:25:46 -0000
Message-ID: <brq3iu$5nfbc$1@ID-131901.news.uni-berlin.de>

"Bob Badour" <bbadour_at_golden.net> wrote in message news:aoCdnbmkVbe0SUKiRVn-tA_at_golden.net...
> Your list of "fundamentals" does not answer any of the questions "What is
> data?", "What does it mean to manage data?" or "What principles facilitate
> or guide effective data management?"

In that case I'd be interested in learning some of these fundamentals. I may have to take myself to the library...

> Of the items in your list above, integrity and data types are fundamental,
> but your elaborations above are anything but fundamental.
>
> One can come up with any number of taxonomies for integrity
> constraints--Chris Date has published enough of them in his career. The
> taxonomy I find most enlightening is: All integrity constraints constrain
> variables. Integrity is fundamental because it is fundamental to the
> manipulation function when managing data.
>
> A data type does not enforce business rules--the integrity function of the
> dbms does this. Data type is fundamental to computing and not only to data
> management. A data type comprises both a set of values and a set of
> operations on those values. With respect to the relational model, Date and
> Darwen have observed that data types define what we can make statements
> about, and relations make statements about them.

Hmmm, I thought Data Types (including UDTs) did enforce business rules, by constraining the set of possible values that can be stored in a column constrained to that type. If a business rule dictates that data of a certain type must fall within a spefic range, for example, then by defining a type that imposes this constraint, the business rule could be enforced by the Data Type?

Thanks for your reply

Tobes Received on Wed Dec 17 2003 - 11:25:46 CST

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