Oracle SQL and PL/SQL Handbook: A Guide for Data Administrators, Developers, and Business Analysts

Entities and Attributes

A database is a representation of a real-world thing called an entity. Examples of entities are vehicles, employees, customers, fish, buildings, and even things such as baseball teams. The database stores facts about the entity in an organized framework, model, or schema. These facts are called attributes.

An instance is one occurrence of an entity. Figure 1.1 illustrates three instances of the entity Student. The facts about the student entity are its attributes. As you can see, we know that one of the students is named Matt and plays baseball (not shown is that he was 9-1 his senior year and won the Nebraska Class B state championship game).

Figure 1.1. Three instances of the entity Student and attributes for the instance ...