DEFINITION OF ERD AND RELATED TERMS.
An ERD , or Entity-Relationship Diagram , is a graphical representation of entities, attributes, and relationships that are involved in a particular domain or system. ERDs are commonly used in database design to model the relationships between entities and their attributes. E ntities in an ERD refer to the objects or concepts that are being modelled. They are represented as rectangles with their name written inside. Attributes are characteristics or properties of the entities and are represented as ovals connected to their respective entity. Cardinalities in an ERD describe the relationships between entities and indicate the number of occurrences of one entity that are associated with a single occurrence of the other entity. Cardinality is represented as a number or symbol on the relationship line between the two entities. Several types of relationships can be represented in an ERD, including: One-to-One (1:1) Relationship : This type of relationship occurs when each occurrence...