CREATE OR REPLACE FUNCTION id_is_good
  (i_student_id IN NUMBER)
  RETURN BOOLEAN
AS
  v_id_cnt NUMBER;
BEGIN
  SELECT COUNT(*)
    INTO v_id_cnt
    FROM student
   WHERE student_id = i_student_id;
  RETURN 1 = v_id_cnt;
EXCEPTION
  WHEN OTHERS
  THEN
    RETURN FALSE;
END id_is_good;

 1 declare
 2    v_local_first_name student.first_name%type;
 3    v_local_last_name student.last_name%type;
 4    rst BOOLEAN ;
 5  begin
 6    rst := id_is_good(&sv,v_local_first_name, v_local_last_name);
 7    dbms_output.put_line(rst);
 8  end;

--如果需要打印，可以这样
if rst then
  dbms_output.put_line('TRUE');
else
  dbms_output.put_line('FALSE');
end if;