Get count of orders created monthly - sql

Question

I'm trying to list the total number of orders for the last 12 rolling months (not including the current month).
This is my query:
Select
Year(CreatedOn)*100+Month(CreatedOn) YearMonth,
Count(*) OrderCount
From Orders
Where DateDiff(MM,CreatedOn,GetUTCDate()) Between 1 And 12
Group By Year(CreatedOn), Month(CreatedOn)
Order By YearMonth
As expected, I am getting the results correctly. However, when there are no orders in a specific month, the month is excluded from the result completely. I would like to show that month with 0. See sample result:
201809 70
201810 8
201811 53
201812 67
201901 15
201902 13
201903 10
201905 12
201908 9
See the missing months 201904, 201906 and 201907. There should be a total of 12 rows.
The query should be executable within a sub-query using For XML Path so that I can get a comma separated list of orders in the last 12 months.
How can I accomplish this?

Answer 1

You need to generate the rows that you want somehow. One method uses a recursive CTE:
with dates as (
select Year(getdate())*100+Month(getdate()) as yearmonth,
1 as n, datefromparts(year(getdate()), month(getdate()), 1) as yyyymm
union all
select year(dateadd(month, -1, yyyymm)) * 100 + month(dateadd(month, -1, yyyymm),
n + 1,
dateadd(month, -1, yyyymm)
from cte
where n < 12
),
q as (
<your query here>
)
select d.yearmonth, coalesce(q.orders, 0) as orders
from dates d left join
q
on d.yearmonth = q.yearmonth;

Answer 2

Check this-
WITH R(N) AS
(
SELECT 1
UNION ALL
SELECT N+1
FROM R
WHERE N < 12
)
SELECT REPLACE(LEFT(CAST (DATEADD(MONTH,DATEDIFF(MONTH,0,(DATEADD(MONTH,-N,GetUTCDate()))),0) AS DATE),7),'-','') AS [YearMonth],ISNULL(o.OrderCount,0) as OrderCount
FROM R A
LEFT JOIN
(
Select
Year(CreatedOn)*100+Month(CreatedOn) YearMonth,
Count(*) OrderCount
From Orders
Where DateDiff(MM,CreatedOn,GetUTCDate()) Between 1 And 12
Group By Year(CreatedOn), Month(CreatedOn)
) O ON O.YearMonth=REPLACE(LEFT(CAST (DATEADD(MONTH,DATEDIFF(MONTH,0,(DATEADD(MONTH,-N,GetUTCDate()))),0) AS DATE),7),'-','')
Order By REPLACE(LEFT(CAST (DATEADD(MONTH,DATEDIFF(MONTH,0,(DATEADD(MONTH,-N,GetUTCDate()))),0) AS DATE),7),'-','');