Configure an Aggregator transformation to perform aggregate calculations, such as averages and sums, against groups of data. You can use an Aggregator transformation to remove duplicate rows.
The Aggregator transformation behaves like the Expression transformation except you can configure the Aggregator transformation to perform calculations on a group of data. The Expression transformation returns results on a row-by-row basis.
For example, you can use the Aggregator transformation to calculate the average salary for employees in each department of an organization. In the Aggregator transformation, create a group for the department number and then configure an expression to calculate the average salary for the employees in each group.