Web Database Applications with PHP, and MySQL

Entity-Relationship Modeling

Entity-relationship (ER) modeling is a simple and clear method of expressing the design of database. ER modeling isn’t new—it was first proposed by Chen in 1976—but it has only emerged as the dominant modeling paradigm for databases in the past 10 or 12 years.

Figure C-2 shows a partial model of the winestore. In this diagram, you can see the relationship between wines, wineries, and regions. Each wine has attributes such as a name, type, and a description. A wine is made by a winery, and each winery has attributes such as a name, phone, and description. Many wineries are located in a region, where a region has a map and description.

Figure C-2. A simple ER model showing the relationship between wines, wineries, and regions

ER diagrams aren’t complicated, and we have already illustrated most of the features of ER modeling in Figure C-2. These features include:

Rectangles

Represent entities—that is, objects being modeled. Each entity is labeled with a meaningful title.

Diamonds

Represent relationships between entities; a relationship is labeled with a descriptive title that represents how the entities interact.

Ellipses

Represent attributes that describe an entity.

Lines

Connect entities to relationships. Lines may be without any annotation, be annotated with an M and an N, or annotated with an M and a 1 (or an N and a 1). Annotations indicate the ...