The Aggregator transformation lets you define groups for aggregations, rather than performing the aggregation across all input data. For example, rather than finding the total company sales, you can find the total sales grouped by region.

To define a group for the aggregate expression, select the appropriate input, input/output, output, and variable ports in the Aggregator transformation. You can select multiple group by ports to create a new group for each unique combination. The Integration Service then performs the defined aggregation for each group.

When you group values, the Integration Service produces one row for each group. If you do not group values, the Integration Service returns one row for all input rows. The Integration Service typically returns the last row of each group (or the last row received) with the result of the aggregation. However, if you specify a particular row to be returned (for example, by using the FIRST function), the Integration Service then returns the specified row.

When selecting multiple group by ports in the Aggregator transformation, the Integration Service uses port order to determine the order by which it groups. Since group order can affect the results, order group by ports to ensure the appropriate grouping. For example, the results of grouping by ITEM_ID then QUANTITY can vary from grouping by QUANTITY then ITEM_ID, because the numeric values for quantity are not necessarily unique.

The following Aggregator transformation groups first by STORE_ID and then by ITEM:

If you send the following data through this Aggregator transformation:

The Integration Service performs the aggregate calculation on the following unique groups:

The Integration Service then passes the last row received, along with the results of the aggregation, as follows: