Re: Uniqueness, NULLs and design options

either will work. which approach selected depends on the nature of the application and how it interacts with the data.

"ks" <usenet_spam_at_online.no> wrote in message news:3b1103ed.22595851_at_news.online.no...
> Three tables; articles, authors and the intermediary table
> article_authors linking the two first in a many-to-many relationship.
>
> Now, an article may have several authors. BUT only one "main" author
> who gets most of the credit. And the articles are ordered
> alphabetically by this authors name in the physical archives.
>
> Now, should I add another column to the article table - pointing
> directly to the one main author. That means two parallel relationships
> between articles and authors.
> Or, is there a way of enforcing one single "main" author in the
> intermediary table by adding a column ? The table would then have
> author_id, article_id and main. Most rows would have a NULL, but for
> each article there must be ONE author flagged as "main" - no more, no
> less.
Received on Wed May 30 2001 - 23:38:46 CEST