Running Sum in SQL Server

Running Sum in SQL Server

As a Programmer\developer we are aware of Fibonacci Sequence where the  next number is found by adding up the two numbers before it.
for e.g.-0, 1, 1, 2, 3, 5, 8, 13, 21, 34, ...

In SQL we termed it as Running Total or RunningSum where we will add a new Column that will calculate the Running total.

CREATE TABLE RunningTotal (
   Product nvarchar(100),
   P_Cost int not null
)


INSERT INTO RunningTotal (Product,P_Cost) VALUES ('X',100),('X',150),('X',200),('X',250),('X',300);
INSERT INTO RunningTotal (Product,P_Cost) VALUES ('Y',1000),('Y',1500),('Y',2000),('Y',2500),('Y',3000);
INSERT INTO RunningTotal (Product,P_Cost) VALUES ('Z',10),('Z',15),('Z',20),('Z',25),('Z',30);


So below is the Script calculating Running Sum (Fibonacci Sequence in a New Column ) and  Running Sum Per Product.

Below Script will calculate two below Columns

1. Total Running Sum-Running Total of  P_cost for all Product irrespective of Product
2. Running Sum Per Product-Running Total of each Product Calculating Running Sum for Each Product

with cte as
(
Select Product,P_cost,row_number()over(order by (Select 0))as RowNum
 from RunningTotal b
 )
 select Product,P_cost ,(Select Sum(P_cost) as TotalRunningSum from cte a where a.RowNum<=b.rownum    ) as TotalRunningSum,
(Select Sum(P_cost) as TotalRunningSum from cte a where a.RowNum<=b.rownum and a.Product=b.product    ) as RunningSumPerProduct
from cte b
order by Product

Output

NOTE: I have Used row_number()over(order by (Select 0))as RowNum to get row_number of each Row if your table has an identity column then you can use it Replacing this.