Do you absolutely need foreign keys in a database?

Question

I was wondering how useful foreign keys really are in a database. Essentially, if the developers know what keys the different tables depend on, they can write the queries just

Answer 1

Perhaps the question should be "How bad are orphan records?". In many cases orphaned records aren't really going to hurt anything. Yes these records may persist until the end of time but how bad is this really? Cascading updates or deletes are rarely useful features. Referential integrity sounds nice but I think is not as important as we have been lead to believe. The biggest benefit to FK's is the documentation they provide. In my experience FK's for referential integrity are way more trouble than they are worth.