An Entity Relationship Diagram is a visual representation of the relationship between entities in a process and creates a structured database. They can be used to document existing databases, develop new ones, or identify any issues within those that already exist. Being able to interpret the steps in a system in different ways allows for a greater understanding of the operations.
There are two types of ERD notations:
Chen’s notation → this notation is visually similar to swimlanes in its’ use of shapes to create a diagram. Entities are indicted by rectangles and represent a noun. Circles are used to describe the attributes of an entity (adjectives or characteristics). Diamonds are used to describe the relationship between symbols (verb).
Crow’s Foot notation → this notation creates a box for each entity, then lists the attributes below in the same box. Entities contain a unique identifier called the primary key (PK) that cannot be shared between multiple values. Relationships can be one-to-one, one-to-many, or many-to-many, and is determined by whether there is a crow’s foot represented at the end of the connectors.
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