After you understand the problem that you are trying to solve with your C/SIDE application, the next task is to divide the information that you want to store in the database into basic categories such as customers, products, employees, and so on.
Before you create the tables, you should define a data model. The data model must describe:
-
The tables in the database.
-
The fields in the tables.
-
The relationships between the fields in your tables.
-
Constraints for fields and relationships.
The Entity-Relationship (ER) model is a tool for defining a data model.
An ER model can map real-world situations to a relational database system such as C/SIDE.
An ER model divides all the elements of a real world situation into two categories: entities and relationships. An entity is a "thing" in the real world with an independent existence. An entity may be an object with a physical existence, such as a particular car or person, or it may be an object with a conceptual existence, such as a company or a job. Relationships describe how the entities are related.
To use the ER model, you must complete the following steps:
-
Identify the types of entities associated with the problem that you are trying to solve. Create tables to represent each of these types of entities.
-
Identify the properties of each type of entity and create fields in the tables to represent each of these properties.
-
Identify the relationships between the entities and add these relationships to the tables.
The following topics provide an overview of the ER model and illustrate the benefits of applying a formalized design method.