Month Year Issue

March 2002 Issue: 24

Journal of Conceptual Modeling
www.inconcept.com/jcm

What's Wrong with this Picture?
Test Your Database Knowledge
by Fabian Pascal

This is a first in a series of articles that will present quotes each from some industry source (article, exchange, product claim, etc.) that indicates a fundamental fallacy/misconception in data management. The quotes are presented for your debunking. The best debunkings setting the record straight, receives a copy of Fabian's latest book - "Practical Issues in Database Management - A Reference for the Thinking Practitioner"

Here is the first set of quotes -

1. “The more you drift away from any physical implementation, the more performance is going to suffer ... The choice is between best logical structure or best physical structure, or a compromise.”

2. “Ironically, there is really no difference between a document and a database -- In both cases, you have to abstract information and a certain amount of metadata that helps the system understand the meaning and uses of that extracted information ... XML could put an end to that by breaking down the traditional barriers between document and database processing. Interactive Web applications have characteristics of both ... Running an auction on a Web site is a massive database challenge ... But it's also a massive document processing challenge, because you have to offer all the descriptions of all the products and so on.”

3. “I am designing a database system but I am a little unsure about normalization - could anyone tell me if the information below is in third normal form? If it isn't could anyone suggest where I've gone wrong.

Protocol (ProtocolRef,Title,GuidelineLink,URL,
Format,Category,Abstract)
Users (ProtocolRef,UserNo)
UserProfile(UserNo,FirstName,Surname,E-mail,HomeHospital,NHSTrust,Position)
Comments (ProtocolRef,UserNo,DateMade,MainBody)
Dates (ProtocolRef,DateCreated,NextReview,LastReview)
Author (ProtocolRef,FirstName,Surname,Publisher)
OtherAuthors (ProtocolRef,FirstName,Surname)
Watermark (ProtocolRef,AuthorityScore,Organisation)
OtherProtocols (ProtocolRef,Title,RelatedProtocolRef)
where ProtocolRef and UserNo are key fields.”

4. “I am having difficulty creating a table with one of the columns in a composite primary key being NULL[able]. Example: table ABC with columns in the PK ' A' NOT NULL, ' B' NOT NULL, and ' C' NULL. Logically, I have a valid business reason for wanting to implement a table with at least one column of the compound PK being nullable.”

5.“In creating a database, normalization is the process of organizing it into tables in such a way that the results of using the database are always unambiguous and as intended. Normalization may have the effect of duplicating data within the database and often results in the creation of additional tables. (While normalization tends to increase the duplication of data, it does not introduce redundancy, which is unnecessary duplication.) Normalization is usually a refinement process after the initial exercise of identifying the data objects that should be in the database, identifying the relationships and defining the tables required and the columns within each table.

Debunk one, some or all - enjoy the adventure and determine why something is wrong.

The web site www.dbdebunk.com will give you some insight into debunking. Remember you are debunking - you are not supporting the quote. However, if you insist, then support the idea.

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Fabian Pascal ,Editor, Publisher and Co-Founder -
is an independent industry analyst, consultant, author and lecturer specializing in database management. He was affiliated with Codd and Date, has taught seminars and advised US and foreign user and vendor organizations on database technology, strategy and design. Author of two books, he contributed extensively to most industry publications.