select distinct t2.dt,
       max(t1.price) over(partition by t2.dt) high,
       min(t1.price) over(partition by t2.dt) low,
       trunc(avg(t1.price) over(partition by t2.dt), 2) bal,
       min(t1.price) keep(dense_rank first order by t1.datatime) over(partition by t2.dt) open,
       max(t1.price) keep(dense_rank last order by t1.datatime) over(partition by t2.dt) close,
       max(t1.db) keep(dense_rank last order by t1.datatime) over(partition by t2.dt) db2
  from t1 ,(
  select to_date('2012-06-11 13:00:00', 'yyyy-mm-dd hh24:mi:ss') -
       (level - 1) * 3 / 1440 dt
  from dual
connect by level <= 21
  ) t2 where t1.datatime>=t2.dt-3/1440 and t1.datatime<t2.dt