Tips for Specifying Relationships

The following tips are useful to keep in mind as you add relationships to your model:

• The relationships you define in a model must reflect corresponding implementations in the data source, as well as the features supported by the adaptor your model uses. Enterprise Objects doesn’t know, for example, if your adaptor supports left outer joins, so you need to be careful with regard to the characteristics you set for relationships.
• Use the diagram view to quickly create pairs of inverse relationships by Control-dragging between source and destination attributes.
• Use the Relationship Inspector to specify information about a relationship, such as whether it’s to-one or to-many, its semantics (join type), the destination model, and the destination entity in the destination model.
• Relationships can be compound, meaning that they can consist of multiple pairs of connected attributes. You can specify additional pairs of attributes only in the Relationship Inspector. Simply select a second source attribute and a second destination attribute and click Connect a second time.
• A to-one relationship from one foreign key to a primary key must always have exactly one row in the destination entity—if this isn’t guaranteed to be the case, use a to-many relationship. This rule doesn’t apply to a foreign key to primary key relationship where a null value for the foreign key in the source row indicates that no row exists in the destination.
• To-one relationships must join on the complete primary key of the destination entity.