Toad World® Forums

Exclusive Ors (Xors among relationships)


I’d like to re-raise the issue of exclusive or (xor) relationships such that:

Each vehicle must be at one and only one facility XOR each vehicle must be on one and only one route. This is often shown as an arc on a logical data model diagram. In the transition to PER, this would be translated to two foreign key columns with a trigger that would enforce the presence of exactly one of the two FK columns. I read the workaround in an earlier post, but that workaround suggests that the two entities are subtypes of a third–which is redirecting the “reality” from the relationships (where it belongs) to the entities.


Hello Mike,

Thank you for reaching out. We will look into this, but we are also going to need some time to review this issue properly. Once we reach some conclusion, I will make sure to let you know (next week at the latest).





thank you for your feedback. In Toad Data Modeler you can take advantage of inheritance defined as Exclusive and set the generation to N-1 (Each child inherits the Parent), but I believe you already know that. Modeling of Arcs is not supported and currently not planned, however I created change request for the requirement: TDM-1222.

Please feel free to add the feature suggestion to IdeaPond!

Thank you,