How do I model a ternary relationship in Database Design Studio?
As a deliberate choice, Database Design Studio does not have a ternary relationship type. This is because we believe that a ternary relationship can be better modeled using a Weak Entity as we discuss below. As an example consider this scenario: The relationship attendance is a ternary relationship between the three entities, and clearly must be a table, with its primary key made up of the primary keys from the 3 entities to which it is related. If you make attendance a weak entity, with Weak Relationship to all of the three other entities you will achieve the desired end result of a “ternary” type of relationship, as shown in the ERD below: The Data Structure Diagram using the rules of the ERD is shown below: As you can see, Database Design Studio can model a ternary relationship by breaking it down to binary relationships and using a weak entity and Weak Relationships.
