Yes. From the release notes: 2002-06-17 (2.5.0), "Parse (but do not implement) foreign keys." At one point there was also a tool which would generate trigger

Yes. From the release notes: 2002-06-17 (2.5.0), "Parse (but do not implement) foreign keys." At one point there was also a tool which would generate trigger rules to enforce foreign key constraints. (2008 Oct 15 (3.6.4), Added the source code and documentation for the genfkey program for automatically generating triggers to enforce foreign key constraints)