I have this sample table:
Product | Category | QTY | Load Date
-----------+---------------+-------------+--------------
1 Alpha 10 Jan. 1, 2021
2 Beta 20 Jan. 1, 2021
3 Charlie 20 Jan. 1, 2021
1 Alpha 30 Jan. 2, 2021
3 Charlie 30 Jan. 3, 2021
1 Alpha -50 Jan. 4, 2021
2 Beta -20 Jan. 4, 2021
4 Delta 40 Jan. 4, 2021
I want to add a column that will sum the quantity base on Previous Load Date, and group by Product and Category.
How can I come up with an output as shown below?
Product | Category | QTY | Load Date | Sum_QTY
-----------+---------------+-------------+---------------+----------
1 Alpha 10 Jan. 1, 2021 10
2 Beta 20 Jan. 1, 2021 20
3 Charlie 20 Jan. 1, 2021 20
1 Alpha 30 Jan. 2, 2021 40
3 Charlie 30 Jan. 3, 2021 50
1 Alpha -50 Jan. 4, 2021 -10
2 Beta -20 Jan. 4, 2021 0
4 Delta 40 Jan. 4, 2021 40
Your help means a lot.
Thank you