SQL - Building iteration table - sql

Question

I have a problem with table's iteration. There is status product (test_product) in stock and actions: add or remove from stock.
product
action
operation_date
number
total
test_product
add
2023-01-03
4
4
test_product
remove
2023-01-05
-3
1
test_product
remove
2023-01-07
-1
0
In some day we have add or remove product, number of product and total number.
I want to count number of days, where total number is 0 in some period, let's say from 2023-01-01 to 2023-01-10 with starting value of total column is 0.
In my mind I have table like this:
calendar_day
product
action
operation_day
number
total
2023-01-01
0
2023-01-02
0
2023-01-03
test_product
add
2023-01-03
4
4
2023-01-04
4
2023-01-05
test_product
remove
2023-01-05
-3
1
2023-01-06
1
2023-01-07
test_product
remove
2023-01-07
-1
0
2023-01-08
0
2023-01-09
0
2023-01-10
0
Counting of 0 days is technical operation, it's not important now. Problem is building table.
I've tried something like this:
GO
DECLARE #PRODUCT AS VARCHAR(30)
SET #PRODUCT = 'test_product'
DECLARE #TOTAL AS INT
SET #TOTAL = 0
DECLARE #STOP_DATE AS DATE;
SET #STOP_DATE = CAST('2023-01-10' AS DATE)
DECLARE #UP_DATE AS DATE;
SET #UP_DATE = CAST('2023-01-01' AS DATE);
WHILE #STOP_DATE >= #UP_DATE
BEGIN
SELECT
#UP_DATE AS calendar_day,
CASE
WHEN operation_date = #UP_DATE THEN operation_date
ELSE ''
END AS operation_date,
number,
#TOTAL+number AS total
FROM stock
JOIN products ON products.id = stock.product_id
WHERE products.name = #PRODUCT
AND stock.operation_date >= #UP_DATE
AND stock.operation_date <= #UP_DATE
SET #UP_DATE = DATEADD(DAY, 1, #UP_DATE)
END
But I've got separation result, 7 of them are empty and it's too slow, because we have 9000 items for now.
Can you help me?

Answer 1

You can accomplish to this task into three steps:
build a calendar table with a recursive query, that stops at calen_date < '2023-10-01'
left join the calendar table with your products table
compute a running sum on your number value to get your total.
WITH calendar AS (
SELECT CAST('2023-01-01' AS DATE) AS calendar_day
UNION ALL
SELECT DATEADD(DAY, 1, calendar_day) FROM calendar WHERE calendar_day < '2023-01-10'
)
SELECT calendar_day, product, action_, operation_date, number,
SUM(COALESCE(number,0)) OVER(ORDER BY calendar_day) AS total
FROM calendar c
LEFT JOIN test_product p
ON c.calendar_day = p.operation_date
Output:
calendar_day
product
action
operation_day
number
total
2023-01-01
0
2023-01-02
0
2023-01-03
test_product
add
2023-01-03
4
4
2023-01-04
4
2023-01-05
test_product
remove
2023-01-05
-3
1
2023-01-06
1
2023-01-07
test_product
remove
2023-01-07
-1
0
2023-01-08
0
2023-01-09
0
2023-01-10
0
Check the demo here.