Output Fields
When you connect upstream transformations to a Union transformation, you initialize the output fields. The initial output fields are an exact copy of the input fields in group1.
When you define output fields, note the following:
- •After you initialize the output fields, you cannot change the output fields by connecting or disconnecting the input group.
- •You can manually add output fields if you add them before you connect one of the Union transformation input groups.
- •If you connect the Union transformation to an upstream transformation that does not pass in any fields, the output fields are not initialized.
- •At run time, the mapping passes null values to output fields that are not in a field mapping.