Need to Count Items in PO

Question

I want to count the items monthly wise those are using first time in that year (APR - MAR).
For example if we use a item for PO in the month of April, May, June, .... the item should count in the month of April only
I developed one query for that
but it takes more time to run
SELECT nvl(po.no,0) New_Items,to_char(trunc(mths.dt,'MM') , 'MON-YYYY') Items_Month from
(select count( distinct a.item_id) no ,to_char(trunc(a.transaction_date,'MM'),'MM-YYYY') Monthly from
(select rsl.item_id, rt.transaction_date
from rcv_transactions rt
, rcv_shipment_lines rsl
where rt.shipment_line_id=rsl.shipment_line_id
and rt.transaction_type='RECEIVE'
and rt.transaction_date between nvl(:P_FROM_DATE, rt.transaction_date) and nvl(:P_TO_DATE, rt.transaction_date)
and rsl.item_id not in (select rsl.item_id
from rcv_transactions rt
, rcv_shipment_lines rsl
where rt.shipment_line_id=rsl.shipment_line_id
and rt.transaction_type='RECEIVE'
and rt.transaction_date < nvl(:P_FROM_DATE, rt.transaction_date))) a
group by to_char(trunc(a.transaction_date,'MM'),'MM-YYYY')) PO
, (SELECT add_months('01-DEC-2006', lvl) dt
FROM (select level lvl
from dual
connect by level < 1000)) mths
WHERE to_char(trunc(mths.dt,'MM'),'MM-YYYY')=po.Monthly(+)
and mths.dt between :P_FROM_DATE and :P_TO_DATE
order by mths.dt
please help to solve this issue
Adina

Answer 1

Something like this?
select count(distinct item_id) new_items,
       the_month
  from (select item_id,
               to_char(the_date,'yyyymm') the_month
               first_value(to_char(the_date,'yyyymm')) over (partition by item_id order by the_date nulls last) first_month
          from your_table -- or < your query >
where the_month = first_month
group by the_month*** not tested ***
Regards
Etbin