EMCS 6th batch

Judge yourself

Recursive-Relationship-ER-Diagrams

Cardinality-ER-Diagrams

Multivalued-Attribute-ER-Diagrams

Entity

An entity can be a person, place, event, or object that is relevant to a given system. For example, a school system may include students, teachers, major courses, subjects, fees, and other items. Entities are represented in ER diagrams by a rectangle and named using singular nouns.

Weak Entity
A weak entity is an entity that depends on the existence of another entity. In more technical terms it can defined as an entity that cannot be identified by its own attributes. It uses a foreign key combined with its attributed to form the primary key. An entity like order item is a good example for this. The order item will be meaningless without an order so it depends on the existence of order.

ER Diagram Symbols and Notations