Oracle SQL Analytic dotaz – rekurzivní průběžný součet podobný tabulkovému procesoru

Pojďme tedy uvolnit MODEL klauzule (zařízení, jehož tajemství je překonáno pouze jeho silou) o tomto problému:

with data as (
  select date'2012-01-01' as mm,    800 as a from dual union all
  select date'2012-02-01' as mm,   1900 as a from dual union all
  select date'2012-03-01' as mm,   1750 as a from dual union all
  select date'2012-04-01' as mm, -20000 as a from dual union all
  select date'2012-05-01' as mm,    900 as a from dual union all
  select date'2012-06-01' as mm,   3900 as a from dual union all
  select date'2012-07-01' as mm,  -2600 as a from dual union all
  select date'2012-08-01' as mm,  -2600 as a from dual union all
  select date'2012-09-01' as mm,   2100 as a from dual union all
  select date'2012-10-01' as mm,  -2400 as a from dual union all
  select date'2012-11-01' as mm,   1100 as a from dual union all
  select date'2012-12-01' as mm,   1300 as a from dual
)
select mm, a, b
from (
  -- Add a dummy value for b, making it available to the MODEL clause
  select mm, a, 0 b
  from data
)
      -- Generate a ROW_NUMBER() dimension, in order to access rows by RN
model dimension by (row_number() over (order by mm) rn)
      -- Spreadsheet values / measures involved in calculations are mm, a, b
      measures (mm, a, b)
      -- A single rule will do. Any value of B should be calculated according to
      -- GREATEST([previous value of B] + [current value of A], 0)
      rules (
        b[any] = greatest(nvl(b[cv(rn) - 1], 0) + a[cv(rn)], 0)
      )
 

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