Union Transformation in Informatica

The Union transformation is an Active, Connected non-blocking multiple input group transformation use to merge data from multiple pipelines or sources into one pipeline branch. Similar to the UNION ALL SQL statement, the Union transformation does not remove duplicate rows.

You can connect heterogeneous sources to a Union transformation. The Union 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 Custom transformation. 

The Union transformation is a non-blocking multiple input group transformation. You can connect the input groups to different branches in a single pipeline or to different source pipelines.

When you add a Union transformation to a mapping, you must verify that you connect the same ports in all input groups. If you connect all ports in one input group, but do not connect a port in another input group, the PowerCenter Server passes NULLs to the unconnected port.

Below image shows a mapping with a Union transformation: 

By default in the Union transformation properties the active property is enabled and cannot be edited. 

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