oracle sysdate 等 時間的相關應用

select t.task_id as counts
  from tnm_task_info t
 where (t.is_valid = 2 and
       to_date(t.start_time, 'yyyy-mm-dd hh24:mi:ss') <= sysdate and
       t.start_time is not null)
   and (to_date(t.end_time, 'yyyy-mm-dd hh24:mi:ss') >= sysdate and
       t.end_time is not null)
   and (to_date(t.send_param, 'hh24:mi') <= sysdate and
       t.last_update_dt < trunc(sysdate))
   and ((t.send_type = 'D' or
       (t.send_type = 'M' and t.send_time = to_char(sysdate, 'DD')) or
       (t.send_type = 'W' and
       t.send_time = to_char(to_number(to_char(sysdate, 'D')) - 1))))
 order by t.insert_dt