oracle sql计算用时

declare 
time_before binary_integer;
time_after  binary_integer;
begin
  time_before :=DBMS_UTILITY.get_time();
  FOR i IN 1..2 LOOP
    dbms_lock.sleep(1);--休眠函数，要有管理员权限才能执行
  END LOOP;
  time_after :=DBMS_UTILITY.get_time();
  DBMS_OUTPUT.put_line('所用的时间为：'||(time_after-time_before)*1000);
END;