select *
  from t_standard_dtl d
 where trim(d.acc) = '111111'
   and trim(d.sub) = '6'
   and d.txn_type = '2'
   and d.confirm_flag = '0'
   and d.txn_date || d.txn_time =
       (select max(txn_date || txn_time)
          from t_standard_dtl
         where trim(acc) = '111111'
           and trim(sub) = '6'
           and d.txn_type = '2'
           and d.confirm_flag = '0')

select *
  from (select *
          from t_standard_dtl d
         where trim(d.acc) = '111111'
           and trim(d.sub) = '6'
           and d.txn_type = '2'
           and d.confirm_flag = '0'
         order by max(txn_date || txn_time) desc) 
 where rownum <2;

------解决方案--------------------
同楼上，是返回2条日期最大的两条记录吧

------解决方案--------------------
不要让别人接受你的思路,建议把原数据和结果数据贴出来!

------解决方案--------------------

SQL code
select *
  from t_standard_dtl d
 where trim(d.acc) = '111111'
   and trim(d.sub) = '6'
   and d.txn_type = '2'
   and d.confirm_flag = '0'
   and d.txn_date || d.txn_time =
       (select max(txn_date || txn_time)
          from t_standard_dtl
         where trim(acc) = '111111'
           and trim(sub) = '6'
           and d.txn_type = '2'
           and d.confirm_flag = '0')

-- 上面的SQL可以看出：既然父查询和子查询是查的同一个表，
-- 那么你这样的话，需要析取两次：父查询析取一次、子查询析取一次!(如果你的表有1000万行记录，析取后，只有1000条记录)

-- 我们可以用表别名，这样只需要对原表析取一次
with a as ( select *
             from t_standard_dtl d
             where trim(d.acc) = '111111'
              and trim(d.sub) = '6'
              and d.txn_type = '2'
              and d.confirm_flag = '0' )
select a1.*
from a a1 where exists (select 1 from a a2
                        having max(a2.txn_date)=a1.txn_date
                        and    max(a2.txn_time)=a1.txn_date );