SUM
The SUM function returns the sum of all numbers in the arguments, which can be numbers or node references.
Syntax
sum(value1,[value2]....)Arguments
value1 – The first node or number to be added. This is a required argument.
value2,...– The additional nodes or numbers to be added. These are optional arguments.
Example
sum(COLUMN1, COLUMN2)Returns the sum of COLUMN1 and COLUMN2