ERD or Entity relationship diagram is the most common database design and modelling tool used in System Design phase. The diagram basically represents all data entities of the targeted system, their attributes and relationships. Database modeler represents ERD in various levels of details such as Context Data Model, Key based model and Fully attributed model. Fully attributed model could be used as the blueprint logical model for implementing the physical database design. Below are some sample ERDs for an IT shop that provide service for its client -
Entity Definition (This is developed first prior to any modelling):
Context Data Model:
Key Based Model:
Fully Attributed Model:
