An aggregate expression can include conditional clauses and functions that are not aggregate functions. The aggregate function can also include an aggregate function nested within another aggregate function, such as:

MAX( COUNT( ITEM ))

The aggregate expression result varies based on the group by ports in the transformation. For example, the following aggregate expression finds the total quantity of items sold:

SUM( QUANTITY ) 

However, if you use the same expression, and you group by the ITEM port, the Data Integration Service returns the total quantity by item.

You can create an aggregate expression in any output port and use multiple aggregate ports in a transformation.