Running total for grouped data SQL - sql

Question

I know there are a lot of questions about this and I have tried a lot of the answers but none have worked for me yet (see below for the most promising).
I want to get the running total in the column amount grouped by project and date divided into two groups (invoiced or costs). The group is dependent on the Cost Center as you can see in the query.
This topic has seemed to be the closest to what I'm trying to achieve but I cant get it to work.
SQL - running total when data already grouped
With the code below I get the error message "Column 'M3FDBPRD.MVXJDTA.FGLEDG.EGAIT2' is invalid in the select list because it is not contained in either an aggregate function or the GROUP BY clause." But I don't want to group by cost center in the result, I only want to use it to group the amount.
The reuslt im trying to achevie is this (if using the data above):
My current code is this:
SELECT
Project As Projektnr,
LastDayOfMonth,
-SUM(CASE WHEN CostCenter= '9000' THEN Amount
WHEN CostCenter = '2100' THEN Amount
WHEN CostCenter = '2200' THEN Amount
WHEN CostCenter = '2300' THEN Amount END) OVER (ORDER BY LastDayOfMonth) AS Invoiced,
-SUM(CASE WHEN CostCenter > '9000' and CostCenter < '9999' THEN Amount END) OVER (ORDER BY LastDayOfMonth) AS RunningTotalCosts
FROM [M3FDBPRD].[MVXJDTA].[FGLEDG]
WHERE Project = '150001'
GROUP BY LastDayOfMonth, Project
ORDER BY LastDayOfMonth
I have SQL Server version 13
Thank you

Answer 1

You are mixing window functions and aggregation. The logic looks like:
SUM(SUM(CASE WHEN CostCenter IN ('9000' '2100', '2200', '2300')
THEN Amount
END)
) OVER (ORDER BY LastDayOfMonth) AS Invoiced,
SUM(SUM(CASE WHEN CostCenter > '9000' and CostCenter < '9999'
THEN Amount
END)
) OVER (ORDER BY LastDayOfMonth) AS RunningTotalCosts
That is, the SUM()s need to nested. The inner SUM() is the aggregation. The outer SUM() is the window function.