XPath can only deal with certain amount of operators but not with ‘+’.
So you will need to create variables (ie. totalGroup & totalCapacity) before the retrieve and doing your necessary calculation beforehand.. Then in the xpath you can use $totalGroup and $totalCapacity.
However, that solution won’t work because I want to put a constraint on the database and not create a variable.
I tried making a third database attribute, RoomCapacity = AdultsCapacity + ChildrenCapacity, made with a microflow. Still, it did not appear as an option on the XPath of the retrieve on the microflow I am trying to achieve.
as Sjors wrote, you can’t use arithmetic operators within XPath query constraints. It’s allowed to use logical operators only, arithmetic ones are supported in Java code only, please check out the documentation.