Decreasing running total in oracle sql

Question

Table A

Week    Column_1   Column_2
0       9          92
1       0          84
2       1          84
3       4          83

The result I want is

Week Column_1  Column_2  Remaining
0    9         92        83
1    0         84        83
2    1         84        82
3    4         83        78

So, if you notice. I want to calculate the Remaining as Column_2 - Column_1 for week 0 and after week 0 I want to calculate the Remaining as Remaining - Column_1

Is it possible?

Answer 1

You can use this query.

SELECT a.*,
       SUM (CASE
              WHEN a.week = 0 THEN column_2 - column_1
              ELSE -column_1
            END)
         over (
           ORDER BY week )
FROM   tablea a;