Running Total by Group SQL (Oracle)

Question

I have a table in an Oracle db that has the following fields of interest: Location, Product, Date, Amount. I would like to write a query that would get a running total of amount by Location, Product, and Date. I put an example table below of what I would like the results to be.

I can get a running total but I can't get it to reset when I reach a new Location/Product. This is the code I have thus far, any help would be much appreciated, I have a feeling this is a simple fix.

select a.*, sum(Amount) over (order by Location, Product, Date) as Running_Amt
from Example_Table a

+----------+---------+-----------+------------+------------+
| Location | Product | Date      | Amount     |Running_Amt |
+----------+---------+-----------+------------+------------+
| A        | aa      | 1/1/2013  | 100        | 100        |
| A        | aa      | 1/5/2013  | -50        | 50         |
| A        | aa      | 5/1/2013  | 100        | 150        |
| A        | aa      | 8/1/2013  | 100        | 250        |
| A        | bb      | 1/1/2013  | 500        | 500        |
| A        | bb      | 1/5/2013  | -100       | 400        |
| A        | bb      | 5/1/2013  | -100       | 300        |
| A        | bb      | 8/1/2013  | 250        | 550        |
| C        | aa      | 3/1/2013  | 550        | 550        |
| C        | aa      | 5/5/2013  | -50        | 600        |
| C        | dd      | 10/3/2013 | 999        | 999        |
| C        | dd      | 12/2/2013 | 1          | 1000       |
+----------+---------+-----------+------------+------------+

Answer 1

Ah, I think I have figured it out.

select a.*, sum(Amount) over (partition by Location, Product order by Date) as Running_Amt
from Example_Table a

Answer 2

from Advanced SQL Functions in Oracle 10g book, it has this example.

SELECT dte "Date", location, receipts,
SUM(receipts) OVER(ORDER BY dte
ROWS BETWEEN UNBOUNDED PRECEDING
AND CURRENT ROW) "Running total"
FROM store
WHERE dte < '10-Jan-2006'
ORDER BY dte, location

Answer 3

I could type out all the answer or send you to where I learned it. :)

Check this out, it explains exactly what you are trying to do.

http://www.codeproject.com/Articles/300785/Calculating-simple-running-totals-in-SQL-Server