Chapter 10 Building Data Transformation Diagrams

Inserting a data aggregation

A data aggregation performs an aggregation on the data of the incoming flow using functions such as Avg, Min, Max, Count, Sum etc., and thus combines data.

You define a list of columns in the Aggregation Columns tab to specify which columns are used to aggregate the data.

You can modify the data structure columns of a data aggregation. Each data structure column must have an aggregation function defined, except the aggregation column.

To insert a data aggregation:

1. Select the Data Aggregation tool in the palette, and create the corresponding object in the diagram.
2. Select the Data Flow tool, and draw a flow from the preceding step (a data input or action) to the data aggregation to initialize it with the appropriate columns.
3. Double-click the data aggregation symbol to open its property sheet. The Data Structure Columns tab is automatically completed with the values from the incoming flow.
4. Click the Aggregation Columns tab, click the Select Aggregation Columns tool to open a selection dialog box, which allows you to select one or more columns to aggregate. Make your selection, click OK to add the columns and return to the tab, then click Apply.
   
5. Click the Data Structure Column tab and for each column, type an aggregation function in the Source Expression column, or delete unnecessary columns.
6. Click OK to save your changes and return to the diagram.

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