How to join a table which is derived from a with statement into a larger query - sql

Question

I have a large query which joins many different select queries to create a single table with one of the columns recording current stock. I now need to count the out of stock days in the next 99 days but since inbound stock and demand stock do not have a record for every day I have to create a table which shows the movement of stock for each day in the next 99 days by taking current stock plus the change of stock on each future dates. In order to get to this I have created the below stand alone query which returns the correct results for the change in stock per day, the problem that I now face is that I am unable to join this query to main query.
DECLARE #Date date
SET #Date = '2020-12-15'
;WITH cte AS
(
SELECT
CASE
WHEN DATEPART(Day, #Date) = 1 THEN #Date
ELSE DATEADD(day, DATEDIFF(day, 0, #Date) + 1, 0)
END AS myDate,
SKU
FROM
BS_BufferSetting
UNION ALL
SELECT
DATEADD(day, 1, myDate), SKU
FROM
cte
WHERE
DATEADD(day, 1, myDate) <= DATEADD(day, 99, #Date)
)
SELECT
myDate AS Date,
SKU,
ISNULL(Amount_IOP, 0) - ISNULL(Amount_DP, 0) AS Amount
FROM
CTE
LEFT OUTER JOIN
DP_Demand ON SKU = SKU_DP AND mydate = Date_DP
LEFT OUTER JOIN
IOP_Inbound ON SKU = SKU_IOP AND mydate = Date_IOP
The above query returns a result set like this:
Date SKU Amount
----------------------
2020-12-16 BEX -108
2020-12-17 BEX 0
2020-12-18 BEX -12
2020-12-19 BEX 0
Once I have linked this to the main query I will then need to work out how to add in the opening stock (from the main table) and formulate a running total but this is part two of the problem.

Answer 1

You can chain CTE's like this:
;with firstcte as
(
select 1 as MyColumn
),
AnotherCTEUsingTheFirstOne as
(
select MyColumn from firstcte
)
select * from AnotherCTEUsingTheFirstOne
so you should be able to;
DECLARE #Date date
SET #Date = '2020-12-15'
;WITH cte AS
(
SELECT
CASE
WHEN DATEPART(Day, #Date) = 1 THEN #Date
ELSE DATEADD(day, DATEDIFF(day, 0, #Date) + 1, 0)
END AS myDate,
SKU
FROM
BS_BufferSetting
UNION ALL
SELECT
DATEADD(day, 1, myDate), SKU
FROM
cte
WHERE
DATEADD(day, 1, myDate) <= DATEADD(day, 99, #Date)
),
secondCTE As
(
SELECT
myDate AS Date,
SKU,
ISNULL(Amount_IOP, 0) - ISNULL(Amount_DP, 0) AS Amount
FROM
CTE
LEFT OUTER JOIN
DP_Demand ON SKU = SKU_DP AND mydate = Date_DP
LEFT OUTER JOIN
IOP_Inbound ON SKU = SKU_IOP AND mydate = Date_IOP
)
SELECT * FROM ATable A INNER JOIN secondCTE B ON A.Col=B.Col