Binary Relationship Type Constraints
Explore binary relationship type constraints in entity-relationship models, focusing on mapping cardinality like one-to-one, one-to-many, many-to-many, and participation constraints that define entity dependencies and schema rules.
Binary relationship type constraints
In the previous lesson, we learned that there is a degree of relationship that exists between entities. However, sometimes this degree is affected by the constraints of the organization or a particular scenario. Consider, for example, a case where the company has a rule that each employee must work for exactly one department. In this and similar cases, we would like to describe this constraint in our schema. Such rules are usually called the “constraints” on the relationship types that exist in our schema.
These constraints limit the possible combinations of entities that may participate in the corresponding relationship set. There are two main types of binary relationship constraints: mapping cardinality and participation.
Let’s look at each one of them in detail below.