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09/19/23: For the latest on 1NF see: FIRST NORMAL FORM - A DEFINITIVE GUIDE

 

Note: In "Setting Matters Straight" posts I debunk online pronouncements that involve fundamentals which I first post on LinkedIn. The purpose is to induce practitioners to test their foundation knowledge against our debunking, where we explain what is correct and what is fallacious. For in-depth treatments check out the POSTS and our PAPERS, LINKS and BOOKS (or organize one of our on-site/online SEMINARS, which can be customized to specific needs). Questions and comments are welcome here and on LinkedIn.

(Continued from Part 2)

In this part we set matters straight about first normal form (1NF)

What's right/wrong about this database picture?

“A relation is in first normal form (1NF) if (and only if):

• Each attribute contains only one value.
• All attribute values are atomic, which means they can’t be broken down into anything smaller.

In practice, 1NF means that you should not have lists or other composite structures as attribute values. Below is an example of a relation that does not satisfy 1NF criteria:This relation is not in 1NF because the courses attribute has multiple values.

STUDENT-COURSES
==================================================
 STUDENT          COURSES
-=======================--------------------------
 Jane Smith       Databases, Mathematics
 John Lipinsky    English Literature, Databases
 Dave Beyer       English Literature, Mathematics
--------------------------------------------------

To transform this relation to the first normal form, we should store each course subject as a single value, so that each student-course assignment is a separate tuple.”

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Fallacies

It is unknown, based on sheer tabular visualization, whether a relation is in 1NF, namely if attributes have:

• Single or multiple values;
• Atomic or or decomposable values.

Fundamentals

We have defined precisely value atomicity and 1NF throughly and discussed it extensively in multiple posts. Instead of repeating all that here, we refer the reader to them:

First Normal Form in Theory and Practice series
https://www.dbdebunk.com/2016/03/real-data-science-first-normal-form-in.html

Simple Domains and Value Atomicity

How to Think (and Not to Think) During Database Design

Forward to the Past: Out-clevering the DBMS

Setting Matters Straight

Is the relation visualized by the above table in 1NF or not?

Seldom are non-1NF relations designed intentionally in practice these days (but only because, luckily, SQL DBMSs do not support nested relations), and not because practitioners understand what it and value atomicity mean, and the implications. Indeed, as the above example demonstrates, few in the industry -- if any -- understand what value atomicity means in RDM. You can confirm this by testing your knowledge against our references.

Whether a relation is a database relation (i.e., is in 1NF as well as 5NF) cannot be determined by sheer inspection of a tabular display of the body of the relation (its extension), but only in conjunction with the conceptual model the database is intended to represent, which includes the semantic constraints (domain constraints in particular) (the intension of the relation) guaranteeing semantic consistency of the database with that model.

(Continued in Part 4)