A relationship is used in a logical model to show that there is an association or link between two entities, or between an entity and itself. Relationships are represented as one or more foreign key attributes. You can create the following types of relationships in a logical model:
You can also automatically create relationships when you reverse engineer a database with existing relationships.
On the diagram window, each relationship can show the following information:
In a logical model, relationships also display in the Model Explorer, where you can add, review, delete, and modify them. You can also add a relationship using the Relationships editor or the diagram window.
When you add a relationship, the relationship is labeled R_n, where R stands for relationship, and n is a unique number. Each number is assigned only once per model, and new relationship numbers are calculated beginning with the number zero. Foreign key attributes automatically migrate across relationships. Therefore, when you delete a relationship, the contributed foreign key attributes, foreign key columns, or view columns are automatically removed from the child entity, table, or view.
There are a number of options provided that let you quickly navigate between entities in a large model. You can navigate a model using the Go To Parent or Go To Child options from the relationship shortcut menu to proceed to either the parent or child entity for the selected relationship. The portion of the diagram window that contains the parent or child entity for the current relationship is automatically displayed. You can also click a relationship line to highlight it. Highlighting allows you to trace the path of the relationship line from parent to child.
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