text: alter table hdb_feature_property
  add constraint hdb_feature_property_fk1
  foreign key    (feature_id)
  references     hdb_feature(feature_id)
  ;
  
  alter table hdb_feature_property
  add constraint hdb_feature_property_fk2
  foreign key    (property_id)
  references     hdb_property(property_id)
  ;
  
  