The Merge tool returns null values in ArcGIS Pro

Description

In some instances, when using the Browse function in the Merge tool to search for and add input datasets from the local computer file location, null values are returned in the merged results.

The image below shows null values are returned in the attribute table after running the Merge tool.

Cause

This is a known limitation of the Merge tool in ArcGIS Pro.

Solution or Workaround

Use one of the methods below to resolve the issue.

Select the input datasets from the drop-down list

1. In ArcGIS Pro, add data to the Contents pane. Refer to ArcGIS Pro: Add data to a project or ArcGIS Pro: Add layers to a map or scene for instructions.
2. On the top ribbon, click the Analysis tab > Tools.
3. In the Geoprocessing pane, search for and select Merge (Data Management Tools).
4. In the Merge pane, click the Parameters tab.
5. Click the drop-down list next to the Browse icon, and select the desired input dataset for Input Datasets. Repeat the same step until all the required datasets are included. Alternatively, click the Add Many drop-down button to load data from the map.

Note:
Alternatively, drag the datasets from the Contents pane, and drop them in the Input Datasets section in the Merge pane.

6. Fill in the output name for Output Dataset. Configure the Field Map section accordingly, and check the Add source information to output option. Click Run.

Note:
Alternatively, click the Reset  button after adding feature classes and before running the Merge tool.

The image below shows the correct values are returned in the attribute table after running the Merge tool.

Use the Append tool

In ArcGIS Pro, use the Append (Data Management) tool to resolve the issue. Refer to ArcGIS Pro: Append (Data Management) for more information.