Information Modeling and Relational Databases, 2nd Edition

4.2. Uniqueness Constraints on Unaries and Binaries

Unary fact types are the easiest, so let’s look at them first. Suppose that, as part of a fitness application, we record which people are joggers. This can be handled with a unary fact type, as shown in Figure 4.2.

Figure 4.2. A unary fact type with sample population.

For simplicity, let’s again assume we can identify people just by their surname. A sample population is included. From the conceptual viewpoint, the fact population is the set containing the following facts:

The Person with surname ‘Adams’ jogs.
The Person with surname ‘Brown’ jogs.
The Person with surname ‘Collins’ jogs.