declare
i integer;
begin
for i in ( select distinct item_sid from bp)
loop
UPDATE ICP b
SET BP_EFF_IRM = (Select base_eff_irm
                          From  BP a
                          Where a.item = b.item and
                                a.tree = b.tree and
                                a.cell = b.cell and
                                a.map_eff_irm = b.map_eff_irm and
                                b.mth between a.base_eff_irm and a.base_end_irm)
where b.item = i.item;
commit;
end loop;
end;