Need more speed for this query :)

Hi,

I found an interesting article on running totals at
http://www.databasejournal.com/features/mssql/article.php/3112381.

I have converted one to postgresql for my banking account:

-- Subtotals on categories and a GrandTotal
 select *,
      case when a.oid= (select oid from nchecks where a.category
=category order by category desc, oid desc limit 1)
      then (select sum(amount)::text  from nchecks where oid <= a.oid
and a.category=category)
      else '  '
      end as SubTotal,
      case when a.oid = (select oid from nchecks order by category
desc, oid desc limit 1)
       then (select sum(amount) from nchecks)::text
      else '  '
      end as GrandTotal
from nchecks a
order by category ,oid

The account has a 'category' for each transaction and of course an
'amount' for
the transaction ( and some other fields...)

The table does not have any fields defined as keys ( I am using oids
with there being
no chance for overflow...).

With only ~3300 rows the rascal takes its time...

explain begins with...
Sort  (cost=626576.75..626584.96 rows=3283 width=181).....

Is there any way to get this puppy running a bit faster?

Jerry