I need help writing a query that shows the amount of orders for each month of the year and also the cumulative amount each year - sql

Question

I am so close to answering this question, but can't figure out the final bits.
I am using the AdventureWorks2019 database.
My code is:
with cte as
(
Select
year(orderdate) as "Years",
month(orderdate) as "Months",
sum(SubTotal) as "MonthlySales",
datepart(m, orderdate) as "MonthNumber"
from sales.SalesOrderHeader
group by year(orderdate), month(orderdate)
)
select
Years, Months, MonthlySales as "MonthlySales", sum(MonthlySales) over (partition by months order by MonthlySales
rows between unbounded preceding and current row) as "Cumulative"
from cte
group by Years, Months, MonthlySales
ORDER by Years, Months
I cant figure out how to order the 'over' part of the query. I know it needs to be "rows between unbounded preceding and current row", but because MonthlySales is sum(totaldue), adding it to another SUM() probably messes it up.
Honestly this question is pretty tough, and I gave it my best.
Thank you for your help!

Answer 1

You can use a window function directly in the aggregation:
Select year(orderdate) as Years, month(orderdate) as Months,
sum(SubTotal) as MonthlySales,
case when grouping(month(orderdate)) = 0
then sum(case when month(orderdate) is not null then sum(SubTotal) end) over (partition by year(orderdate) order bymonth(orderdate))
end as YTD_MonthlySales
from sales.SalesOrderHeader
group by grouping sets (
(year(orderdate), month(orderdate)),
(year(orderdate))
);

Answer 2

Please check and it'll return desired output.
-- SQL SERVER
SELECT t.OrderYear
, CASE WHEN t.OrderMonth IS NULL THEN 'Grand Total' ELSE CAST(t.OrderMonth AS VARCHAR(20)) END b
, t.MonthlySales
, MAX(t.cum_total) cum_total
FROM (SELECT
YEAR(OrderDate) AS OrderYear,
MONTH(OrderDate) AS OrderMonth,
SUM(SubTotal) AS MonthlySales,
SUM(SUM(SubTotal)) OVER (ORDER BY YEAR(OrderDate), MONTH(OrderDate) ROWS UNBOUNDED PRECEDING) cum_total
FROM Sales.SalesOrderHeader
GROUP BY GROUPING SETS ((YEAR(OrderDate), MONTH(OrderDate)))) t
GROUP BY GROUPING SETS ((t.OrderYear
, t.OrderMonth
, t.MonthlySales), t.OrderYear);
Also Check data from https://dbfiddle.uk/?rdbms=sqlserver_2019&sample=adventureworks&fiddle=e6cd2ba8114bd1d86b8c61b1453cafcf