ER model is a diagram used to analyze the structure of a database. There are sets of an entity which represent the tables. Moreover, it shows the relationship among tables that allows you to identify the interactions between entities. In other words, this helps you see what’s going on with your database allowing you to fix issues like discovering missing data. In the following paragraphs, we will look at the ERD examples, notations, and a guideline to draw your own ER model.
Free Downloadable ER Diagrams Examples and Tutorials
An entity-relationship diagram consists of three basic elements such as entity, relationship, and attribute. Along with these are more components based on their main elements like weak entity, multi-valued attribute, and many more. Other notations used to make ERD diagram examples include cardinality and ordinality to define relationships in numbers. Here are brief explanations about each component.
Entity- this represents the name of an object, person, thing, event, or place where data is stored. This is usually represented by rectangles.
Weak Entity- unlike a strong entity that is defined by its attributes, a weak entity solely depends on the existence of another entity.
Attribute- refers to the unique characteristic or property of an entity.
Derived Attribute- refers to an attribute derived or based on another attribute.
Multivalued Attribute- a type of attribute that can have multiple value.
Relationship- defines the interaction between two entities.
Cardinality- this refers to the occurrences of a relationship. In particular, it specifies the maximum number of relationships within two entities.
Ordinality- describes whether a relationship is mandatory or optional. It is also used to determine the absolute minimum number of relationships.
5 Downloadable ERD Examples
If you want to draw entity relationship diagram example, here are some examples to easily get started.
- Hospital Management System ERD Example
This example illustrates how a hospital manages the bill of a patient. There are four entities in the entity-relationship diagram. This includes patient, procedure, physician, and insurance company. Each entity contains a list of attributes to describe its characteristics.
- Software Engineering ERD Example
This is an ERD diagram example application for an enrollment system. It gives the reader an idea that a student can have one or many courses, there’s only one seat allotted for a student, a teacher can have one or many courses to handle, and so on and so forth.
- Car Rental System ERD Example
ERD examples are also helpful for business information systems like car rental system. This helps you visualize and analyze data or discover and identify issues when designing a new system.
- Database ERD Example
This provides an overview of how an ERD of an actual database looks like. With it, you can easily understand the structure of a database. Moreover, this template will help you how to identify the primary key and foreign key attributes.
- Chen ERD Example
You may also visualize a database using Chen notations just like the given entity relationship diagram example above. This is especially useful for teaching-learning situations as well as for the presentation of data.
How to Make ERD Diagram Online?
Now that you learned the essentials of an ER diagram, it’s time to try it yourself. You can actually design this diagram manually but an ER diagram tool will help you save time and effort. GitMind provides the elements and icons to create many types of UML diagrams including ER diagrams. That said, here are the steps to make your own ERD diagram example.
- Launch GitMind on your website and open the flowchart editor by clicking the “New Flowchart” button from the templates page.
- Analyze the data structure of the existing system you want to visualize. After that, insert rectangles to represent the entities and add text to put a label.
- Now insert lines between entities and label them to show the relationships. In other cases, you could also insert a diamond shape on top of the line. Add the attributes of entities by grabbing some ovals.
- Add cardinality by identifying whether the relationships are 1-many, many to many, or 1-1. Finally, export the ERD diagram example to an image or PDF file.
Since you have an idea about the ER notations, examples, and guidelines, you should be able to draw this diagram with ease. Plus, with GitMind, you will be able to create a bunch of diagrams for visualizing the data or processes of a system.