Question

I have a database scheme with versioning data rows, e.g.
Table Person has the columns

id (int, PK)
name (String)
current (Bool)
firstid (int)

Current is 0 for previous data, 1 for the latest entry. All rows for the same entity have the same FirstID, which points to the first ID of the set.

Referencing table: Adress with the same principle:

id (int, PK)
street (String)
person_id (int)
current (Bool)
firstid (int)

Person_id points to patient.firstid. So firstid is never unique, only if current=1

My problem is: I would like to add referential integrity to my tables, but this only works, if the referenced column (patient.firstid) is unique…

Answer 1

You should look at refactoring your table structure. But to keep within the current structure, add a self-referencing foreign key to person

firstid references person(id)

Then, reference the “base person” from the address table

address.person_id references person(id) — which should ONLY store a link to the first id