[Informatica] Union Transformation

Union Transformation

::Transformation type::

Union Transformation is used to merge data form multiple pipeline to form a single pipeline. All the rows from all the input pipelines pass though the Union Transformation. Its noteworthy that Union Transformation DOES NOT remove duplicates. This makes Union a Active transformation. You can Union as many pipelines / sources in a single Union Transformation. However, such is not the case with a Join Transformation.

::Union Groups::
-    As soon as you add a single input pipeline / source to the Union Transformation. The Designer automatically adds output ports groups to the Union Transformation. One cannot edit/delete the output port.
-    The Groups tab displays the Input groups. All the input pipelines appear in this tab. One can rename the groups based on their convention. 
-    The Group Ports displays the column name along with datatype, scale and precision. 

-    The participating sources in a Union must have same number of columns.
-    The datatype, precision and scale for the input ports must match exactly.
-    As discussed earlier, Union Transformation is similar to Union All operation and does not remove duplicate values. However, to do so, you can add a Filter Transformation or alternatively a Router Transformation.

-    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.
- One can join heterogeneous sources to the Union Transformation ie. a Flat file, Table etc to form a single pipeline. The only condition is to keep the number of columns, datatype and precision the same.

The following example shows union of table1 and table2 with diffrent tabs for Uniion transformation.
The below image highlights how a new group can be added and renamed.