* Combines partial foreign keys into singular key
*/
protected ForeignKey combineForeignKey(Map<FKMapKey, ForeignKey> fkMap,
ForeignKey fk) {
FKMapKey fkmk = new FKMapKey(fk);
ForeignKey baseKey = fkMap.get(fkmk);
// Found the FK, add the additional column
if (baseKey != null) {
baseKey.addColumn(fk);
return baseKey;