CREATE OR REPLACE FUNCTION dem.add_person(_lastname text, _firstname text, _gender text)
	-- you may prefer to change the arguments to add day of birth instead of gender
  RETURNS integer AS -- returns dem.identity.pk of newly created person
$BODY$
DECLARE
	_id integer;
BEGIN
	-- name already there ?
	select into _id id from dem.names where firstnames = _firstname and lastnames = _lastname;
	if FOUND then
		RAISE EXCEPTION 'This name already exist.'
		USING HINT = 'Name ID: ' || _id::text ;
	end if;
	-- no, insert new identity and name
	INSERT INTO  dem.identity (gender) VALUES(_gender);
	INSERT INTO dem.names (id_identity, firstnames, lastnames) VALUES (currval('dem.identity_pk_seq'), _firstname, _lastname);
	if FOUND then
		return currval('dem.names_id_seq');
	end if;
	return NULL;
END;$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;
ALTER FUNCTION dem.add_person(text, text, text)
  OWNER TO "gm-dbo";