[vbezhenar]

> For example audit logs get no FKs, when a delete happens the audit logs about the deletion shouldn't be deleted.

    on delete set null

?

[Diggsey]

That still modifies the audit log, which is presumably supposed to be immutable. It also means you lose information, eg. if this is a user ID, then before you would be able to determine if two audit actions were done by the same (deleted) user. With "set null", you can't determine that anymore.

The parent's point is that the choice should depdend on the situation. Sometimes a foreign key is appropriate, sometimes it is not.