Breakdown SUM of INT by Each Month - tsql

Question

Query I use to find the total spend per station for a year. How do I break down the spend of each product by month i.e. each month as a column?
e.DT is a datetime, but only gets populated once a month.
select s.StationID, sum(e.Spend)
from Station s with(nolock)
join Expenditure e with(nolock)
on e.ProductID = s.ProductID
where e.DT between '1 JAN 18' and '1 DEC 18'
group by s.StationID
order by sum(e.Spend) desc

Answer 1

It would be much easier to report your month/year data points as separate rows, rather than columns. I suggest the following query:
SELECT
s.StationID,
LEFT(CONVERT(varchar, e.DT, 120), 7) AS ym,
SUM(e.Spend) AS total_spend
FROM Station s WITH(nolock)
INNER JOIN Expenditure e WITH(nolock)
ON e.ProductID = s.ProductID
WHERE e.DT BETWEEN '2018-01-01' AND '2018-12-01'
GROUP BY
s.StationID,
LEFT(CONVERT(varchar, e.DT, 120), 7)
ORDER BY
s.StationID,
SUM(e.Spend) DESC;

Answer 2

Try with PIVOT this way:
select ProductID, [1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]
from (
select Spend, month(DT) m, ProductID
from Expenditure
where DT between '1 JAN 18' and '1 DEC 18'
) r
PIVOT
( sum(Spend)
for m in ([1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12])
)
AS PivotTable;