Oracle Moving Average without Current Row

Question

Would like to calculate moving average in oracle for the last 30 records excluding current row.

select crd_nb, flng_month, curr_0380,
avg(curr_0380) over (partition by crd_nb order by flng_month ROWS 30 PRECEDING) mavg
from us_ordered

The above SQL calculates moving average for 30 records including current row.

Is there any way to calculate moving average excluding current row.?

Answer 1

select 
  crd_nb, 
  flng_month, 
  curr_0380,
  avg(curr_0380) over (
    partition by crd_nb 
    order by flng_month 
    ROWS between 30 PRECEDING and 1 preceding
  ) mavg
from us_ordered

Answer 2

@be_here_now's answer is clearly superior. I'm leaving mine in place nonetheless, as it's still functional, if needlessly complex.

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An answer would to be to get the sum and count individually, subtract out the current row then divide the two results. It's a little ugly, but it should work:

SELECT crd_nb,
       flng_month,
       curr_0380,
         (  SUM (curr_0380)
            OVER (PARTITION BY crd_nb 
                  ORDER BY flng_month ROWS 30 PRECEDING)
          - curr_0380)
       / (  COUNT (curr_0380)
            OVER (PARTITION BY crd_nb 
                  ORDER BY flng_month ROWS 30 PRECEDING)
          - 1)
          mavg
FROM   us_ordered

If curr_0380 can be null, you'd have to tweak this slightly so that the current row is removed only if it's not null.