How to get cumulative sum in SQL Server (Z=Z+A+B-C)

Question

I want to create cumulative sum in table ( Commul_table) in SQL such as Z=Z+ (A+B-C )

Answer 1

You can use analytic function in this case with rows unbounded preceding (to get sum values before current row)

Select id, A,B,C,sum(A+B-C) over(order by Id rows unbounded preceding) as Z
From Table

Answer 2

It's still a Cumulative Sum, just based on a calculation on three columns:

sum(a+b-c) over (order by Id rows unbounded preceding)

See fiddle

Answer 3

I'm answering to point out that the window frame clause is not needed in most databases. Assuming that the id is unique:

select ct.*, sum(a + b - c) over (order by id) as z
from Commul_table;

If id can be duplicated, please explain what you want for the results. The above also assumes that a, b, and c are never NULL. If they can be, then you want to substitute 0 for them:

select ct.*,
       sum(coalesce(a, 0) + coalesce(b, 0) - coalesce(c, 0)) over (order by id) as z
from Commul_table;