Recursive SQL query - using results from query within query

Question

I'm running SQL Server 2012, and here's what I need:

Row      Field1          Field2
 1         0               1
 2         ?               2
 3         ?               -5

I need a query that will go throw row by row. It should take row2,field1 and set it equal to row1,field1+row2,field2

It then would take row3,field1 and set it equal to row2,field1+row3,field2

Initially the table has values in Field1 that are all equal to 0, and so when I run my query it just always uses 0 for the field1 values.

Any help would be appreciated. I was thinking a CTE would be the way to go, but I just don't know where to go with that.

Edit: Just to clear up some things, in my example. The initial input would be

Row      Field1          Field2
 1         0               1
 2         0               2
 3         0               -5

The desired output would be:

Row      Field1          Field2
 1         1               1
 2         3               2
 3         -2               -5 

My actual table is a bit complicated, but I know I can apply it specifically if I could understand how to pull it off with this example.

Answer 1

Is this what you need? (Unclear if when you refer to row2,field1 for example you mean the before or after update value)

CREATE TABLE YourTable
  (
     Row    INT,
     Field1 INT NULL,
     Field2 INT
  )

INSERT INTO YourTable
VALUES      (1,0,1),
            (2,0,2),
            (3,0,-5); 
WITH CTE AS
(
SELECT *,
       SUM(Field2) OVER (ORDER BY Row ROWS UNBOUNDED PRECEDING) AS RunningTotal
FROM  YourTable    
)
UPDATE CTE 
SET Field1 = RunningTotal

SELECT *
FROM YourTable

Final Result

Row         Field1      Field2
----------- ----------- -----------
1           1           1
2           3           2
3           -2          -5

Or another (more literal) interpretation of your word problem might be

WITH CTE AS
(
SELECT *,
       LAG(Field2) OVER (ORDER BY Row) AS PrevRowField2
FROM  YourTable    
)
UPDATE CTE 
SET Field1 = PrevRowField2 + Field1
WHERE PrevRowField2 IS NOT NULL

Answer 2

Something like this adapted from TSQL A recursive update?

With cte As (
  Select
    Row, 
    Field1, 
    Field2
  From
    t
  Where
    Row = 1
  Union All
  Select
    t.Row,
    t.Field2 + c.Field1,
    t.Field2
  From
    t
      Inner Join
    cte c
      On t.Row = c.Row + 1
)
Update
  t
Set
  Field1 = c.Field1
From
  t
    inner join
  cte c
    On t.Row = c.Row

http://sqlfiddle.com/#!6/cf843/1