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:
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Example
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 |
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See Also
Create Relationships | One-to-One Relationships | One-to-Many Relationships | Entity Diagram