Learn more on what and how to make an ER diagram. These hands-on examples of the diagrams are available in best quality for you to print. ER or entity–relationship diagram describes inter-related things of interest in a specific domain of knowledge. This diagram shows the relationships of entity sets stored in a database. An entity in this context is a component of data. In other words, ER diagrams illustrate the logical structure of databases. Take a look at the example of an ER diagram provided below.
At first glance an entity relationship diagram looks very much like a flowchart diagram. It is the specialized symbols, and the meanings of those symbols, that make it unique. As you can notice in the ER diagram above, an Entity can be any object, place, person or class. In E-R Diagram, an entity is represented using rectangles. Weak entity is an entity that depends on another entity, represented by double rectangle. An Attribute describes a property or characteristic of an entity. An attribute is represented using eclipse. Key attribute represents the main characteristic of an Entity. It is used to represent Primary key. Ellipse with underlying lines represent Key Attribute. An attribute can also have their own attributes. These attributes are known as Composite attribute. A Relationship describes relations between entities. Relationship is represented using diamonds. Follow more examples of the diagrams in the following pictures.
ER Diagrams are most often used to design or debug relational databases in the fields of software engineering, business information systems, education and research. They mirror grammatical structure, with entities as nouns and relationships as verbs. ER diagrams are related to data structure diagrams (DSDs), which focus on the relationships of elements within entities instead of relationships between entities themselves. ER diagrams also are often used in conjunction with data flow diagrams (DFDs), which map out the flow of information for processes or systems.
In making an ER diagram, examine relationships between entities closely: are they necessary? are there any relationships missing? eliminate any redundant relationships; don’t connect relationships to each other. All pictures presented are the printable examples of ER diagrams. You can also find other educational diagrams in the other posts in this site by browsing it in our search column or categories!