函式索引的問題

select coalesce(sum(b.amount * t.goods_price), 0)
   from emall_order            t,
        emall_trade             s,
        ioss_out_depository    a,
        ioss_prod_relation_out b
  where t.tid = s.tid
    and s.status in ('trade_finish', 'wait_buyer_confirm_goods')
    and a.relation_num = s.tid
    and a.status = 'out_finished'
    and b.out_dep_id = a.id
    and a.type = 'out_sales'
    and t.goods_instance_id = 2685
    and a.gmt_out_dep >= to_date('2009-9-11', 'yyyy-MM-dd')
    and a.gmt_out_dep < to_date('2009-10-13', 'yyyy-MM-dd') + 1

    select * from emall_order
   
   
    create index IDX_OUT_DEPOSITORY_GMT_OUT_DEP on IOSS_OUT_DEPOSITORY(to_date(GMT_OUT_DEP,'yyyy-MM-dd'));
   
    drop index IDX_OUT_DEPOSITORY_GMT_OUT_DEP
   
    select * from IOSS_OUT_DEPOSITORY
    where GMT_OUT_DEP > to_date('2010-10-11','yyyy-mm-dd')

select to_date(gmt_out_dep,'yyyy-mm-dd hh24:mi:ss') from IOSS_OUT_DEPOSITORY