A nested aggregate function is an aggregate function within another aggregate function.
For example, the following expression sums sales and returns the highest number:
MAX( SUM( SALES ))
You can include multiple single-level or multiple nested functions in different output fields in an Aggregator transformation. You cannot include both single-level and nested functions in an Aggregator transformation.
You cannot nest aggregate functions in advanced mode.
When an Aggregator transformation contains a single-level function in any output field, you cannot use a nested function in any other field in that transformation. If you need to create both single-level and nested functions, create separate Aggregator transformations.