Ah, that makes sense. So something like: select whatever from thingy, relation, widget where thingy.id = relation.id1 and widget.id = relation.id2

Ah, that makes sense. So something like: select whatever from thingy, relation, widget where thingy.id = relation.id1 and widget.id = relation.id2 and relation.type1 = 'thingy' and relation.type2 = 'widget'