Re: Normalization and N-ary relations

URL type is an intrinsic property of the URL. In a fully normalized database, you would reference the urltype table from the url table -- not from the peopleurl table.

Strictly speaking, the urltype table is not necessary -- you can use:
...

WHERE url.url like 'mailto:%'
...

to restrict your result to email addresses.

That said, you might find that your queries run faster if you add redundant data in the form of a url_type column in peopleurl; however, this will slow down updates and can lead to update anomalies.

Unfortunately, current database products are very weak when it comes to physical independence, and as a result, you might find that you must accept the update problems to achieve other performance requirements. Received on Sun Oct 22 2000 - 06:00:15 CEST