Hello frogcoder, Yes, I use FK's for non-trivial systems. Personally, I believe in the enforcement of FK's via DDL as they document the schema and serve their intended purpose of maintaining data integrity according to the rules of the schema. Enforcing constraints and any other system constraint is part of system design. From a debugging perspective, I would rather have the RDBMS return an integrity error when the layers using it don't follow the rules, instead of chasing down where the contraint was not enforced in every layer.