E-R diagram

The E-R diagram (entity-relation) is a diagrammatical representation of a data model based on a perception of the real world that consists of a collection of basic objects called entities and of relationships among these objects. It is widely used in database design. The E/R diagram was introduced by P P Chen. An entity is a tangible object that exists in the real world, about which some relevant information may be stored. The qualities of an entity which can be stored as information are called the attributes. For example, if teacher is an entity then the teacher’s ID, name, etc. are all its attributes. An association among several entities is called a relationship.