Foreign Key column mapped to multiple primary keys

Question

I have a database which has three tables

Messages - PK = MessageId
Drafts - PK = DraftId
History - FK = RelatedItemId

The History table has a sin

Answer 1

Is there a name for this relationship?

There is no standard name that I'm aware of, but I've heard people using the term "generic FKs" or even "inner-platform effect".

Is it just bad design?

Yes.

The reason: it prevents you from declaring a FOREIGN KEY, and therefore prevents the DBMS from enforcing referential integrity directly. Therefore you must enforce it trough imperative code, which is surprisingly difficult.

Is there a better way to design this relationship?

Yes.

Create separate FOREIGN KEY for each referenced table. Make them NULL-able, but make sure exactly one of them is non-NULL, through a CHECK constraint.

Alternatively, take a look at inheritance.