\pset null NULL

SELECT '<http://foo.bar#1>'::rdf_iri = '<http://foo.bar#1>'::rdf_iri;
SELECT '<http://foo.bar#1>'::rdf_iri = '<http://foo.bar#2>'::rdf_iri;
SELECT '<http://foo.bar#1>'::rdf_iri = NULL;
SELECT '<http://foo.bar#1>'::rdf_iri = '<http://foo.bar#1>'::text;
SELECT '<http://foo.bar#1>'::rdf_iri = '<http://foo.bar#2>'::text;
SELECT '<http://foo.bar#1>'::text = '<http://foo.bar#1>'::rdf_iri;
SELECT '<http://foo.bar#1>'::text = '<http://foo.bar#2>'::rdf_iri;
SELECT '<http://foo.bar#1>'::rdf_iri = '<http://foo.bar#1>'::rdfnode;
SELECT '<http://foo.bar#1>'::rdfnode = '<http://foo.bar#1>'::rdf_iri;