Update statement taking too much time

Question

Hi All,
I defined a cursor in which there are almost 94 lakh records and i want to update few fields of a table from another table which takes data over a dblink.
my cursor is
cursor c_tpo is
      select t.loc_loc_id,
             t.till_no,
             t.transaction_date,
             t.sales_audit_txn_no,
             t.third_party_order_ref
        from dwt_om_email_addresses t
       where (t.merc_loaded_date_time is null or t.ws_ordered_date_time is null or
             t.copos_ordered_date_time is null)
-- And for loop is
for i in c_tpo loop
    select count(*)
      into ln_count
      from web_sales@nrstp
     where dmw_order = i.third_party_order_ref;
    if ln_count = 1 then
      select date_loaded, order_date, order_date, pkt_ctrl_nbr
        into ld_merc_load_date,
             ld_ws_order_date,
             ld_cop_order_date,
             lc_pkt_ctrl_nbr
        from web_sales@nrstp
       where dmw_order = i.third_party_order_ref;
      update dwt_om_email_addresses t
         set merc_loaded_date_time   = ld_merc_load_date,
             ws_ordered_date_time    = ld_ws_order_date,
             copos_ordered_date_time = ld_cop_order_date
       where t.loc_loc_id = i.loc_loc_id
         and t.till_no = i.till_no
         and t.transaction_date = i.transaction_date
         and t.sales_audit_txn_no = i.sales_audit_txn_no;
  end if;
    ln_count          := 0;
    ln_count_pkt      := 0;
    ld_merc_load_date := null;
    ld_ws_order_date  := null;
    ld_cop_order_date := null;
    ld_pkms_date_time := null;
    lc_pkt_ctrl_nbr   := null;
  end loop;
  -----------The ln_count is used to avoid the exception no_data_found and too_many_rows. How do I speed up the process as it takes 1 hr to update 500 records.
What would be the best approach to achieve this in less time.
Thanks

Answer 1

if you check the your condition some where you have metioned
dmw_order = t.third_party_order_ref
if both of these are unique keys or primary key then there is no problem
but if for there are multiple values edit the query by using
rownum <= 1
update dwt_om_email_addresses t
set (merc_loaded_date_time,ws_ordered_date_time,copos_ordered_date_time) =(select date_loaded, order_date, order_date, pkt_ctrl_nbr from( select date_loaded, order_date, order_date, pkt_ctrl_nbr
                                                                             from web_sales@nrstp
                                                                              where dmw_order = t.third_party_order_ref)
where rownum<=1)
where exists  (select '1'
              from web_sales@nrstp i
              where t.loc_loc_id = i.loc_loc_id
              and t.till_no = i.till_no
              and t.transaction_date = i.transaction_date
              and t.sales_audit_txn_no = i.sales_audit_txn_no
              and (t.merc_loaded_date_time is null or t.ws_ordered_date_time is null or
             t.copos_ordered_date_time is null));and for exists clause there is no problem
Edited by: 810345 on Jun 10, 2011 4:07 PM
Edited by: 810345 on Jun 10, 2011 4:08 PM