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 Data Integration Service then performs the defined aggregation for each group.

When you group values, the Data Integration Service produces one row for each group. If you do not group values, the Data Integration Service returns one row for all input rows. The Data Integration Service returns the last row of each group with the result of the aggregation. You can specify to return a specific row. For example, if you use the FIRST aggregator function, the Data Integration Service returns the first row.

When you select multiple group by ports in the Aggregator transformation, the Data Integration Service uses a port order to determine the order by which it groups. The group order can affect the results. Order the group by ports to ensure the appropriate grouping. You can change the port order after you select the ports in the group/

For example, you might create an output port called Price_Out. The expression for Price_Out is SUM (Qty * Price). You define Store_ID and Item as the group by ports. The transformation returns the total price for each item by store.

The input rows might contain the following data:

Store_ID	Item	Qty	Price
101	battery	3	2.99
101	battery	1	3.19
101	battery	2	2.59
101	AAA	2	2.45
201	battery	1	1.99
201	battery	4	1.59
301	battery	1	2.45

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

Store_Id	Item
101	battery
101	AAA
201	battery
301	battery

The Data Integration Service returns the Store_ID, Item, Qty, and Price from the last row with the sum of (Price * Qty) for each item by store :

Store_ID	Item	Qty	Price	Price_Out
101	battery	2	2.59	17.34
101	AAA	2	2.45	4.90
201	battery	4	1.59	8.35
301	battery	1	2.45	2.45