A One-to-Many relationship between two entities indicates that one record in Entity A corresponds to multiple records in Entity B but one record in Entity B has only one associated record in Entity A. In this situation, the reference attribute must be in the "One side" of the relationship; i.e. in Entity B.

How to implement a One-to-Many relationship:

In the "Many side" entity involved in the relationship, create an attribute of type <Other Entity> Identifier.


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

A Company has one or more Contact. An Contact belongs to a Company.

To implement this relationship, the reference attribute must be in the entity Contact:

Entity Diagram

eSpace tree

See Also

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