What You Need to Know About Entity-Relationship Models

by Aug 7, 2019

An entity-relationship model – also known as an ER Model, ER Diagram or ERD – is a graphical representation of entities and their relationships used in database design.  In our discussion, the designation model and diagram are used interchangeably.

What is an Entity-Relationship Modeling?

Simply put, entity-relationship modeling is a method of data modeling that displays an information system’s entities and their relationships graphically. The concept of an ER model has been around since its introduction by Peer Chen at MIT in 1976 and has proven to be a useful construct. Using an ER diagram can be instrumental in creating high-level logical data models and contribute to good database design.

The elements that comprise an ER model are:

  • Entities, which can be physical items or concepts. A comparison can be made to database tables where each row symbolizes an instance of the entity.
  • Relationships pertain to the interactions between entities. Relationships can be categorized in multiple ways based on how many entities are involved in a relationship. They also carry a cardinality which indicates how many times an entity participates in a relationship. The cardinality can be one to one, many to one, or many to many.
  • Attributes define the properties of specific entities. Attributes come in a variety of types. A key attribute is one that uniquely identifies an entity. Composite attributes are made up of multiple other attributes.

The entities, attributes, and their relationships will be specific to the business process for which you are building the diagram. Now that you know what goes into an ER model, let’s see how you go about creating one.

Creating an Entity-Relationship Model

There is an accepted procedure for creating an ER model. It involves a variable amount of time performing the following steps.

Identifying the entities – This is a critical first step. Properly identifying the entities involved in the ER model lays the groundwork for a viable diagram that can be incorporated into your database design.

Relationship identification – Determining the relationships that the entities will engage in is key to creating your model. Give careful consideration to how the entities involved in your model interact when performing this step.

Determining the cardinality of relationships – You need to understand the number of times that entities participate in relationship to correctly construct the ER diagram.

Identifying attributes – Compiling a list of attributes entails studying an organization’s data. The attributes should be collected without assigning them to specify entities at first. When the list is complete, the attributes should be mapped such that an attribute is paired with only one entity.

Best practices for the development of ER models include:

  • The elimination of redundant relationships or entities.
  • Proper labeling all entities and relationships.
  • Limiting each entity to one appearance in the model.
  • Ensuring the ER diagram you choose to employ can handle all of the data you plan to represent.
  • Not connecting relationships to each other.
  • Highlighting the most important parts of the model with colors.

Benefits of Using an ER Model for Database Development

Several benefits can be bestowed on a database developer by working with ER models and diagrams. Among them are:

Simplicity of design – An ER diagram is created directly from the relationships between entities and attributes. It is a straightforward process that helps you construct your database efficiently.

Visual data representation – An ER model offers a diagram of the logical structure of your database which may uncover modifications that need to be made in compiling your entities or relationships.

Fostering communication – The visual nature of an ER model makes it the perfect vehicle for communication between database team members as well as associated non-technical stockholders.

A viable ER model will facilitate collaboration between database developers and highlight problems in how the underlying data is being handled. Identifying issues early in the development process is always preferred to the hassle of reworking code once the project is underway.

Using an ER Modeling Tool for Better Database Design

Hopefully, we have convinced you as to the utility of using ER diagrams in database development. The question then becomes how to best construct your models. You could probably just get out the scratchpad and start scribbling, but you work in IT and know there must be some tool that can help you out. Well, you’re right on that point.

Aqua Data Studio is a comprehensive database management and development tool that provides DB professionals with a robust ER modeler. It offers all the capabilities you need to create ER models as well as many advanced features that make it even more valuable to your database team. You can easily import tables and views for existing databases into your model and perform reverse engineering to obtain a visual representation of a database’s structure. The tool supports different display levels and can generate HTML reports from your models.

If you think that entity-relationship models can help your database developers, you should strongly consider adding Aqua Data Studio to their software toolbox. It’s a great way to help your team in their search for greater productivity.