通过加索引对sql语句优化

select

substr(a.djxh,6) as id,
(a.nd || a.yf) DECL_YM,
a.zspm_dm as LEVY_ITEM_ID,
b.zsxmmc  as LEVY_ITEM_NAME, --||'--'||d.zspmmc
100 as DECL_STATUS,
a.nsqx_dm as TAX_TERM_CODE,
c.nsqxmc  as TAX_TERM_NAME,
to_char(a.sbqx, 'yyyyMMdd') as DECL_TREM,
to_char(a.sjtb_sj, 'yyyyMM') as DATA_CREATE_YM,
a.sjgsdq as area_code
from
(
select djxh, nd, yf, zspm_dm, nsqx_dm, sbqx, sjtb_sj, sjgsdq,zsxm_dm
from tci.sb_ysbtj
where zfbz_1 is null
or zfbz_1 = 'N'
and exists (select *
from (select to_number('10124' || i.id) as iid
from i_reg_account i
where mgr_dept in
(select t.org_id
from i_organization t
where t.isdirectguanhu = 1
start with (t.org_id = 24300900000)
connect by prior t.org_id = t.parent_id)) d
where djxh = iid)
and trim(yf) = to_char(sysdate, 'MM')
and nd = to_char(SysDate, 'YYYY')

) a left join dm_gy_zsxm b
on a.zsxm_dm = b.zsxm_dm
left join dm_gy_nsqx  c
on a.nsqx_dm = c.nsqx_dm