Union Transformation Overview

By PenchalaRaju.Yanamala

Transformation type:ActiveConnected

The Union transformation is a multiple input group transformation that you use to merge data from multiple pipelines or pipeline branches into one pipeline branch. It merges data from multiple sources similar to the UNION ALL SQL statement to combine the results from two or more SQL statements. Similar to the UNION ALL statement, the Union transformation does not remove duplicate rows.

The Integration Service processes all input groups in parallel. It concurrently reads sources connected to the Union transformation and pushes blocks of data into the input groups of the transformation. The Union transformation processes the blocks of data based on the order it receives the blocks from the Integration Service.

You can connect heterogeneous sources to a Union transformation. The transformation merges sources with matching ports and outputs the data from one output group with the same ports as the input groups.

The Union transformation is developed using the Multigroup External Procedure transformation.

Union Transformation Rules and Guidelines

Use the following rules and guidelines when you work with a Union transformation:

You can create multiple input groups, but only one output group. All input groups and the output group must have matching ports. The precision, datatype, and scale must be identical across all groups.The Union transformation does not remove duplicate rows. To remove duplicate rows, you must add another transformation such as a Router or Filter transformation.You cannot use a Sequence Generator or Update Strategy transformation upstream from a Union transformation.The Union transformation does not generate transactions.

Union Transformation Components

When you configure a Union transformation, define the following components:

Transformation tab. You can rename the transformation and add a description. Properties tab. You can specify the tracing level.Groups tab. You can create and delete input groups. The Designer displays groups you create on the Ports tab.

Group Ports tab. You can create and delete ports for the input groups. The Designer displays ports you create on the Ports tab.

You cannot modify the Ports, Initialization Properties, Metadata Extensions, or Port Attribute Definitions tabs in a Union transformation.

Working with Groups and Ports

A Union transformation has multiple input groups and one output group. Create input groups on the Groups tab, and create ports on the Group Ports tab.

You can create one or more input groups on the Groups tab. The Designer creates one output group by default. You cannot edit or delete the output group.

You can create ports by copying ports from a transformation, or you can create ports manually. When you create ports on the Group Ports tab, the Designer creates input ports in each input group and output ports in the output group. The Designer uses the port names you specify on the Group Ports tab for each input and output port, and it appends a number to make each port name in the transformation unique. It also uses the same metadata for each port, such as datatype, precision, and scale.

The Ports tab displays the groups and ports you create. You cannot edit group and port information on the Ports tab. Use the Groups and Group Ports tab to edit groups and ports.

Creating a Union Transformation

Use the following procedure to create a Union transformation.

To create a Union transformation:

1. In the Mapping Designer, click Transformations > Create. 2. Select Union Transformation and enter the name of the transformation. The naming convention for Union transformations is UN_TransformationName. 3. Enter a description for the transformation. Click Create, and then click Done. 4. Click the Groups tab.5. Add an input group for each pipeline or pipeline branch you want to merge.The Designer assigns a default name for each group but they can be renamed.6. Click the Group Ports tab.7. Add a new port for each row of data you want to merge.8. Enter port properties, such as name and datatype.9. Click the Properties tab to configure the tracing level.10. Click OK.