It is one of the three main components of the Data Provider output-based declarative language.
Sometimes it is necessary to make internal calculations that do not necessarily have to go in the Output itself. Variables are used in this case, in a Data provider Group statement.
<variableName> '=' <Formula>
<Formula> is the same as in Data provider Element statement.
&TotalCustomers = 0
CustomerId = CustomerId
CustomerName = CustomerName
&TotalCustomers = &TotalCustomers + 1
Total = &TotalCustomers