Question

Table data look like this

id val

1 4

2 2

3 1

I want result of subtract valu of val field in one sql statement.
like it should be like 4-2-1 = 1 if order by id asc, 1-2-4 = -5 if order by id desc.

Answer 1

You can declare a variable and increment it in the select statement:

declare @sum float

select @sum = case when @sum is null then value else @sum - value end
from YourTable
order by id

select @sum

To reverse the subtraction order, change order by id to order by id desc.