Accumulate a summarized column

Question

I could need some help with a SQL statement. So I have the table \"cont\" which looks like that:

cont_id     name       weight
----------- ---------- -------         


        

Answer 1

try this

;WITH CTE
AS
(
 SELECT *,
ROW_NUMBER() OVER(ORDER BY wsum) rownum
FROM @table1
 ) 
 SELECT 
 c1.name, 
 c1.wsum,
 acc_wsum= (SELECT SUM(c2.wsum) 
                   FROM cte c2
                   WHERE c2.rownum <= c1.rownum)
 FROM CTE c1;

or you can join instead of using subquery

;WITH CTE
AS
(
 SELECT *,
ROW_NUMBER() OVER(ORDER BY usercount) rownum
 FROM @table1
) 
 SELECT 
 c1.name, 
 c1.wsum,
 acc_wsum= SUM(c2.wsum) 
 FROM CTE c1
 INNER JOIN CTE c2 ON c2.rownum <= c1.rownum
 GROUP BY c1.name, c1.wsum;

Answer 2

So, the best way to do this is using cumulative sum:

select t.*,
       sum(wsum) over (order by wsum desc) as acc_wsum
from (<your summarized query>) t

The order by clause makes this cumulative.

If you don't have that capability (in SQL Server 2012 and Oracle), a correlated subquery is an easy way to do it, assuming the summed weights are distinct values:

select t.*,
       (select sum(wsum) from (<your summarized query>) t2 where t2.wsum >= t.wsum) as acc_wsum
from (<your summarized query>) t

This should work in all dialects of SQL. To work with situations where the accumulated weights might have duplicates:

select t.*,
       (select sum(wsum) from (<your summarized query>) t2 where t2.wsum > t.wsum or (t2.wsum = t.wsum and t2.name <= t.name) as acc_wsum
from (<your summarized query>) t