Help with running totals

I have a query that takes monthly totals and rolls them up to get a balance at a specific time code

eg:

  dt                bucket     mon_ttl    
  ---               ------     -------    
  199903            0192      -172527
  199906            0192       546707
  199909            0192      -278684
  199910            0192      1100139
  199911            0192       495279
  199912            0192     -1690914
  200003            0192      1025431
  200006            0192     -1731678
  200009            0192      1979256
  200012            0192      -1273009

Rolls up like

       DT BUCKET OPEN
--------- ---------- ----------

   199903 0192                0
   199906 0192          -172527 
   199909 0192           374180 (-172527+546707)
   199910 0192            95496  etc...
   199911 0192          1195635
   199912 0192          1690914
   200003 0192                0
   200006 0192          1025431
   200009 0192          -706247
   200012 0192          1273009

I get that using

select dt, bucket, lag(run_ttl,1,0)

   over (order by dt) open
from
 (select dt, bucket, ttl,sum(ttl)
   over (partition by bucket order by dt) run_ttl  from
   mon_tot
   where bucket='0192')

But I want to keep that last balance going forward... eg: if I want the open as at 200301 and 200012 was the last non-null balance
I want to carry that forward.

    200012 0192          1273009
    200101 0192          1273009
    [..]
    200301 0192          1273009

But I need to 'make up' the data going forward

I'm on 9.2.0.3 anyone have any tips/ideas? Received on Mon Apr 05 2004 - 13:11:21 CDT