To calculate values for a single row using the Expression transformation, you must include the following ports:
Input or input/output ports.
Provides values used in a calculation. For example, if you need to calculate the total price for an order, create two input or input/output ports. One port provides the unit price and the other provides the quantity ordered.
Provides the return value of the expression. You enter the expression as a configuration option for the output port. You can also configure a default value for each port.
You can enter multiple expressions in a single Expression transformation by creating an expression for each output port. For example, you might want to calculate different types of withholding taxes from each employee paycheck, such as local and federal income tax, Social Security and Medicare. Since all of these calculations require the employee salary, the withholding category, and may require the corresponding tax rate, you can create input/output ports for the salary and withholding category and a separate output port for each calculation.