I am probably being narrow minded, but if I create a foreign key constraint and a row gets updated or deleted, I lose that connection if the child table's column gets set to NULL.
What is the purpose of intentionally keeping these orphaned rows?
With those rules, consider the following use case:
In this case, an
Most of the use cases I can think of generally are of the form "Well, we could do something different but we felt like doing this instead".