CREATE OR REPLACE FUNCTION public.f_return_random(min integer, max integer)
  RETURNS integer AS
$BODY$
DECLARE 
	min_val integer = min;
	max_val integer = max;
	curr_val integer;
	run_while boolean = TRUE;
BEGIN
	SELECT (random() * max_val)::integer INTO curr_val;
	WHILE(run_while) LOOP
		IF curr_val > min_val AND run_while = TRUE THEN
			run_while = FALSE;
		ELSE
			SELECT (random() * max_val)::integer into curr_val;
		END IF;
	END LOOP;
	RETURN curr_val;
END

$BODY$
  LANGUAGE plpgsql VOLATILE
  COST 100;
ALTER FUNCTION public.f_return_random(integer, integer)
  OWNER TO _postgres;


DO $$
DECLARE upd_rec record;
BEGIN
    FOR upd_rec IN SELECT id_n FROM n WHERE to_char(date_create, 'yyyy')::integer = 2016  LOOP
        UPDATE n SET y = (SELECT f_return_random FROM f_return_random(5,20)) WHERE id_n = upd_rec.id_n ;
    END LOOP;
END$$;