Scripts for  Data Creation

SELECT
   Month_Id,
   TO_NUMBER(SUBSTR(month_id,5)) month_Num,
   Sales_Amount,
   SUM(Sales_Amount)
      OVER(PARTITION BY SUBSTR(month_id,1,4)  
      ORDER BY month_id) sales_total
FROM
   Fact_Sales_Summary 
;


  


By use of PARTITION BY SUBSTR(month_id,1,4) in the OVER(...) windowing 
function, the running total ends at the last valve of the year (201212) 
and starts at the running total from the begining of the new year 
(200301).