> It makes little sense to add a surrogate id and a fk on that surrogate id. It violates data quality and integrity just for a hypothetical situation. I would

> It makes little sense to add a surrogate id and a fk on that surrogate id. It violates data quality and integrity just for a hypothetical situation. I would still almost always use an internal artificial key on top of the external id. If you want to enforce data integrity, you can still enforce uniqueness on the external id. "Stability" of an external identifier is almost always an assumption and one that I've seen fail enough times to want that internal id by default.