Re: Database design

mAsterdam <mAsterdam_at_vrijdag.org> wrote:

>An entity is a thing of interest (old ISO definition).

>Some prefer to talk about relations (or relational variables),
>attributes and tuples.
>Others about tables, columns and rows.
>Though the concepts are different

Which is to say, non-parenthetically:

A relation is NOT a table
An attribute is NOT a column
A row is simply NOT a tuple, to the latter of course, I'd agree.

A relation is a set, which need not be written as a table, to be sure. But in a world of constraints, situation and conditions - in a world a databases and a ng devoted to an aspect of same - I also agree it would be reasonable to speak of relations as tables, attributes as columns, and rows as not . . . entities.

>Yet, neither tables nor relations map to entity types.

The single row is then called - what?

>One relation may have attributese from several entitiy types,

Then an entity type is seen as some unique attribute domain?

>and one entity may have data spread across several relations

Then an entity type is not some unique attribute domain? Received on Wed Feb 22 2006 - 00:09:31 CET