Jared Westover wants a foreign key, but one referencing multiple tables:
Do you like a challenge? If you answered yes, you’re my kind of person. Recently, a developer presented me with a problem: they needed a foreign key reference in one table to associate with multiple other tables. Over the years, I’ve often been asked how to make this situation work. However, achieving this relationship with foreign keys is technically impossible with SQL Server and most mainstream relational database platforms. Since SQL Server restricts foreign keys to referencing a single table, how can we solve this problem?
My immediate answer was “triggers,” which happens to be the solution Jared intentionally omits.
I’d rather go with the multiple association tables approach over multiple indicator types, as the latter requires (n-1) NULLs, where n is the number of indicator types (review types in Jared’s example) and I hate NULL because NULL is the void lying about being a value, sort of like how skim milk is water lying about being milk.