Transformations > Union Transformation > Comparison to Joiner Transformation
  

Comparison to Joiner Transformation

A Union transformation can merge data from two sources but does not combine data based on a join condition or remove duplicate rows, like a Joiner transformation.
The following table identifies some key differences between the Union transformation and Joiner transformation, which also merges data from multiple sources. Factor these differences into your mapping design:
Requirement
Union Transformation
Joiner Transformation
Remove duplicate rows
No. You can use a Router or Filter transformation downstream from the Union transformation to remove duplicates.
Yes.
Combine records based on a join condition
No. The Union Transformation is equivalent to a UNION ALL statement in SQL, which combines data vertically from multiple sources.
Yes. The Joiner transformation supports Normal, Right Outer, Left Outer, and Full Outer JOINs.
Include multiple input groups
Yes. You can define two input groups and one output group.
Yes. You can define two input groups, Master and Detail.
Include heterogeneous sources
Yes.
No.
Merge different data types
All of the source columns must have similar data types. The number of columns in each source must be the same.
At least one column in the sources to be joined must have the same data type.
Generate transactions
No.
Yes.