I am maintaining an inventory in azure SQL DW and want to calculate initial and final stock of a day using T-SQL. Below are the details I have - azure-sqldw

Question

I am maintaining an inventory in azure sql DW and want to calculate initial and final stock of a day. Final stock of previous day will be initial stock for present day and Final stock for present day will be initial stock+Produced-sold. I have details of Produced and Sold quantities. How can I calculate initial and final quantities.
I am able to use lag function, but cant add the calculated value to get the finalqunatity in same query.
The query i wany to write but doestnt work is
Select lag(finalquantity,1) over ( Partition by Productid Order by Date) as Initialqty, (Initialqty+Produced-sold) as finalquantity from table
The finalquantity should come as a initialquantity for next record. I want this to happen recursively.

Answer 1

My answer is directly based up on the second query in the Recursive CTEs section of this answer.
I created an Inventory table as I understood your situation. I am basing my solution around InventoryDate, rather than day of week. The final item I want to mention is that your Initial stock number is coming from the Final stock number of the previous week. However, that must be defined somewhere. I hard-coded it is as the anchor member of the recursive CTE. You may pass it in as parameter or get it using a sub-query.
CREATE TABLE Inventory
(
InventoryDate DATE
, Produced INT
, Sold INT
);
INSERT INTO Inventory
(
InventoryDate
, Produced
, Sold
)
VALUES
('2020-07-20', 10, 8)
, ('2020-07-21', 9, 7)
, ('2020-07-22', 11, 10)
, ('2020-07-23', 10, 10)
, ('2020-07-24', 9, 8)
, ('2020-07-25', 7, 8)
, ('2020-07-27', 12, 14);
WITH y AS
(
SELECT
rn = ROW_NUMBER() OVER (ORDER BY InventoryDate)
, InventoryDate
, Produced
, Sold
FROM Inventory
)
, x AS
(
SELECT
CONVERT(BIGINT, 0) AS [rn]
, DATEADD(DAY, -1, MIN(InventoryDate)) AS [IventoryDate]
, NULL AS [Initial]
, NULL AS [Produced]
, NULL AS [Sold]
, 80 AS [Final]
FROM Inventory
UNION ALL
SELECT
y.rn
, y.InventoryDate
, x.Final AS [Initial]
, y.Produced
, y.Sold
, x.Final + y.Produced - y.Sold AS [Final]
FROM x
INNER JOIN y ON y.rn = x.rn + 1
)
SELECT
x.rn
, x.IventoryDate
, x.Initial
, x.Produced
, x.Sold
, x.Final
FROM x;
Here is the demo of this code.