SELECT * FROM (SELECT T.*, ROWNUM RN FROM ( SELECT * FROM v_trade_query  WHERE (f_create_time >= '2017-03-22 08:00:00') AND (f_create_time <= '2018-03-22 08:00:00') AND f_trader_id=252 ORDER BY f_create_time DESC  ) T WHERE ROWNUM <= 100) WHERE RN > 0 

如上所示，这是某一条sql，请问一下 WHERE RN > 0 最后这个判断rownum是否有必要，在我印象中，rownum是不是从1开始计数的呢？