Chapter 10 Building Data Transformation Diagrams

Inserting a data join

A data join allows the join-up of data incoming from several data flows into one outgoing data flow.

You define a list of join columns with join expressions in the Join Columns tab to specify which columns are used to join data.

You cannot modify the data structure columns of a data join.

To create a join column you must select first and second sources from a column selection of the incoming data structure and specify a join expression.

To insert a data join:

1. Select the Data Join 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 join to initialize it with the appropriate columns.
3. Double-click the data join symbol to open its property sheet. The Data Structure Columns tab is automatically completed with the values from the incoming flow.
4. Click the Join Columns tab and click the Add a Row tool to create a join column.
5. Click the First Source column and select a column from a column selection of the incoming data structure and click the Second Source column to select the second source column for the join.
6. Specify a join expression in the Join Expression column and click Apply.
   
7. [Optional] Click the Data Structure Columns tab and delete one of the two columns you selected for the join.
8. Click OK to save your changes and return to the diagram.

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