Relationship Attributes in ER Diagrams

Can a relationship in an entity relationship diagram have its own key? If not, do we need to make a separate object with this key?


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The only kind of relationship that has its own key would be a many-to-many relationship. The key of this relationship is, naturally, the combination of foreign keys with each of its parents.

If there are other attributes of a relationship, then it is not a relationship at all, it is an entity in itself.

Keys associated with one-to-many (and one-to-one) relationships are found in the child table as foreign keys.



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