Association Mapping

You can define association mapping in the Mapping tab of the association property sheet and select the Add Objects tool to add mapping sources.

Associations defined between entity classes can be mapped to reference keys or tables. In order to define association mapping, you have to add the references keys or tables as mapping sources. When you add reference keys, the tables on their ends will also be added.

Associations can be classified as one-to-one, one-to-many and many-to-many according to multiplicities of ends. And associations can be classified as unidirectional and bi-directional according to navigability of both ends. Associations of different types should be mapped in different ways. We will introduce them in detail in the following sections.

• One-to-One Association Mapping Strategy
  You can map each unidirectional one-to-one association to a reference key. The foreign key should have the same direction as the association.
• One-to-Many Association Mapping Strategy
  Each unidirectional many-to-one association is mapped to a reference that has the same direction as the association.
• Many-to-Many Association Mapping Strategy
  Each many-to-many association is mapped to a middle table and two reference keys that refer to tables mapped by entity classes on the two ends.