The Union transformation is used to merge data from multiple sources. Union is a multiple input, single output transformation. It is the opposite of router transformations, which we discussed earlier. The basic criterion to use a Union transformation is that you should have data with the matching data type. If you do not have data with the matching data type coming from multiple sources, the Union transformation will not work. The Union transformation merges the data coming from multiple sources and does not remove duplicates, so it acts as the union of all SQL statements.

As mentioned, union requires data to come from multiple sources. Union reads the data concurrently from multiple sources and processes the data. You can use heterogeneous sources to merge the data using a Union transformation.

A mapping indicating the Union transformation is shown in the following screenshot:

Working on Union transformation is a little different from other transformations. To create a...