CREATE TABLE r1
( id integer,
  name character varying(64),
  PRIMARY KEY (id) 
);

CREATE TABLE t1
( id integer,
  groupnames integer REFERENCES r1(id),
  PRIMARY KEY (id)
);

CREATE TABLE r2
( id integer,
  name character varying(64),
  PRIMARY KEY (id) 
);

CREATE TABLE t2
( id integer,
  groupname integer REFERENCES r2(id),
  PRIMARY KEY (id)
);