Identify the constructs for diagramming types of relationships.
Diagramming Relationship Types
Like all ER diagrams, the Crowsfoot version provides constructs that
represent each type of entity relationship. These constructs are illustrated below:
Notice that the three-pronged “crowsfoot” symbol is simply a miniaturization of the "many" side of a relationship that we discussed in an earlier module. The "one" side of the relationship is indicated by a short vertical line. The graphic below illustrates a one-to-many relationship and its corresponding Crowsfoot construct.
The following Slide Show illustrates the Crowsfoot constructs for 1:1, 1:N, and unresolved M:N relationships, as well as the same M:N relationship resolved:
Unresolved M:N relationship
Resolved M:N relationship
Crows Foot Notation
The symbols used to indicate the types of participation (mandatory and optional) are placed directly on the lines comprising the relationship constructs, as you will see in the next lesson.
Before moving on to the next lesson, click the link below to check your understanding of the elements of an ER diagram.
Crowsfoot Elements ER Diagram