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Re: Normalization, Natural Keys, Surrogate Keys

From: John Doherty <jdoherty_at_null.com>
Date: Thu, 23 May 2002 22:58:13 -0500
Message-ID: <acke1p$fah$1@slb6.atl.mindspring.net>

Pablo Sanchez <pablo_at_dev.null> wrote in message news:3ce64c2f$1_6_at_news.teranews.com...

> The reason I like singular is that when you do data model validation
> on the cardinality, you speak of an instance/row, not of multiple
> rows. This is why I wouldn't agree with people who say to use plural:
>
> [order] -----> [order_detail]
> (0,N) (1,1)
>
> "An ORDER may or may not have an ORDER_DETAIL"

Put another way, "An element of the set ORDERS is related to zero or one elements of the set ORDER_DETAILS."

And it's not true that we ordinarily wish to speak only of single rows. For example, an element of the set ORDERS might be related to zero or more elements of the set ORDER_DETAILS.

With your nomenclature, you'd have to say something like "An ORDER may have one or more ORDER_DETAIL(s)," which sounds natural in speech, but is awkward in writing.

> "An ORDER_DETAIL must have at least one and at most one ORDER"

Or, "An element of the set ORDER_DETAILS is related to one element of the set ORDERS."

It seems to me that this is the main argument for plural or collective table names, and that it makes sense. When we talk about tables, we're talking about sets, and in everyday use, we talk about those with plural or collective nouns, no matter how many elements they contain (at least in English).

For example, it's perfectly normal to say "the set of integers greater than one and less than three": the fact that the set happens to contain only one element doesn't suggest that we should say "integer" instead of "integers."

--
Received on Thu May 23 2002 - 22:58:13 CDT

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