Crow’s foot notation in ER diagram

Use crows foot notation to represent relationships between entities in an entity relational diagram. Entities are connected by lines, and symbols at the beginning or end of the line describe cardinality.

Relationship types and cardinality:

Symbols in crow’s foot notation

A crow’s foot graphics represents “many” or “infinite”.

crows foot notation - many

A dash (closest to the entity in ERD) represents “one”.

crows foot notation - one

An optional relationship is represented by an empty circle.

crows foot notation - optional

A mandatory relationship is represented by a line.

crows foot notation - mandatory

Example of relationship created in Luna Modeler:

One to one relationship

Change the appearance of the crow’s foot notation

You can display mandatory or optional records in the ER diagram. By default, a one-to-many relationship including crow’s foot notation is created in Luna Modeler. To change it to a one-to-one relationship, do the following.

  • Display the relationship detail.
  • In the Cardinality section, change the settings
  • The crows foot graphic will change accordingly.
one-to-one relationship in ER diagram

Tips for designing the ER diagram

  • Identify all the entities you need. Add them to the ER diagram.
  • Find out which entities are related to other entities and create a relationship. Note: of course not all entities need to have a link to other entities. And some may have multiple links.
  • Each entity should be in the diagram once. In Luna Modeler it is possible to display the same entity differently, on a different sub-diagram.

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