Display quarterly results
I want to display the quarterly results from my invoices. I allready have the formula "quarter(Factuurdatum)" but I don't see how I can get the results. For now my formula is as follows: sum((select Kosten).Bedrag)
But I don't know how I have to complete the formula

Thanks for the feedback, guys  both work but when I use the following formula, I get the results of Q4 2021:
let q := yearquarter(Today());
sum((select Kosten where yearquarter(Factuurdatum) = q).Bedrag)
How can I change the formula so that I can see the results for Q1/2021, Q2/2021, Q3/2021, Q4/2021 and so one? I presume a new formula for each quarter and each year?

The formula is working exactly like Steven said it would, see his ps comment.
If you want to create a formula that finds the current year quarter 1 then you can change either:
let q := 1; < change the value of the variable used in the select statement
sum((select Kosten where yearquarter(Factuurdatum) = q).Bedrag)
or
(remove the variable assignment)
sum((select Kosten where yearquarter(Factuurdatum) = 1).Bedrag) < hard code the quarter number into the select statement

Jarno,
I would create a choice field (in this example called Kwartaal) with 4 choices in order Kwartaal1,Kwartaal2,Kwartaal3 en Kwartaal4. With this, you can choose which quarter you want to show. The formula would then be:
let q := Kwartaal;
sum((select Kosten where year(Factuurdatum) = year(today()) and quarter(Factuurdatum) = q).Bedrag)
Steven

Thx guys, but it still does not work I'm afraid. Could ik be because my summary table is a different table than the expenses table? The hierarchy is as follows:
1. Werven (=Construction sites)
1.a) Kosten (=Expenses)
1.b) Vorderstaten (=Progress states)
2. Samenvatting (=Summary)
I tried to get the summary on the "Samenvatting" table where I want to create a dashboard of some sort.