Hello,

We do a lot of fairs and events and we use point of sale to record all sales in fairs.
I created an app to manage fairs. 
In a fair I linked with a one to many relation all sessions from the point of sale.
In the session I added a many to one relations so I link the session to the fair.

So... Is there a way to make a sum of a column in the one to many relation?
I have all sales amounts in it, and I would like to just have the sum  of them. 

(current Version V12)