The Entity Relationship Diagram (ERD) gives a graphical overview of the database. ERDLab There are numerous patterns and sorts of ER Diagrams. A a good deal-used notation is the 'crowfeet' notation, wherein entities are represented as rectangles and the relationships among the entities are represented as traces among the entities. The signs on the quit of the traces imply the form of relationship. The aspect of the connection that is obligatory for the alternative to exist could be indicated through a dash on the line. Not obligatory entities are indicated thru a circle. "Many" is indicated thru a 'crowfeet'; the connection-line splits up in three lines.