A Many-to-Many relationship between two entities indicates that one record in Entity A corresponds to multiple records in Entity B and a record in Entity B can have more than one associated record in Entity A. In this situation, you must create a third entity with, at least, two reference attributes for Entity A and Entity B. A Many-to-Many relationship is, in fact, two One-to-Many relationships with this third entity.

How to implement a Many-to-Many relationship:

Create a third entity with, at least, two attributes:

  • one attribute with the type <Entity A> Identifier

  • another attribute with the type <Entity B> Identifier.


Suppose, that in a business logic, you have these entities:

A Contact can move from Company. In turn, a Company can have more than one Contact.

To implement this relationship, a third Entity must be created, CompanyContact, with at least the following attributes:

Entity Diagram

eSpace tree



See Also

Create Relationships | One-to-One Relationships | One-to-Many Relationships | Entity Diagram