Data Modeling: Special Relationships

1. One to One Relationship
One-to-one relationships are between two entities where both are related to each other, once and only once for each instance of either

For example, one developer is given one development server, but not all development servers are given to the developers








2. Many to Many Relationship

In a many-to-many relationship, multiple occurrences of one entity are related to one occurrence of another, and vice versa.

For example, one developer can assign to many data warehouse development projects and one project can assign to many developers.






Associative entities (also known as intersection entities) are entities used to associate two or more entities in order to reconcile a many-to-many relationship.






3 Recursive Relationships

A recursive relationship is an entity that is associated with itself.

For example, an engineering manager manages a group of engineers. This engineering manager is reporting to the director of engineering who manages many engineering manager. This director ,in term, is also managed by the Vice President of engineering.
















Data,Information, Knowledge and Life