# Union data

Another way to [transform](../transforms-overview/index.md) and structure your data in Pipeline Builder is to apply a union. A union combines two datasets to include all rows from each dataset. In Pipeline Builder, a union retains all rows, including duplicates.

## Select datasets

To union two datasets together, select the first dataset node in your workspace and select **Union**.

![Screenshot of union selection](../../../assets/8081958fb619509744b11d13b31ca35cc1b47f8d069ac911163f17413cd80417.webp)

The first selected dataset is the **Left** side dataset. Select another dataset node to be the **Right** side dataset. Select **Start** to navigate to the union output preview page.

![Screenshot of union selection](../../../assets/8081958fb619509744b11d13b31ca35cc1b47f8d069ac911163f17413cd80417.webp)

### Union multiple datasets

To union more than two datasets in a single transform, you can use one of the following methods:

* **Union board:** Drag multiple input datasets into the union board, which accepts an unlimited number of inputs.
* **Multi-select:** Drag to select all the datasets you want to union, then select the **Union** button.

Both methods allow you to combine many datasets at once without creating multiple sequential union operations.

## Preview a union

In the preview pane, select **Create union**, then view the output dataset preview.

![Screenshot of union selection](../../../assets/0f3f934ec10488426ee27634159633741202034775927a05e9bb6294d10dd73e.webp)

A union requires that all inputs have the same schema. If input schemas do not all match, the union will display an error message with a list of missing columns.

To resolve, remove the references to the missing columns or review your input.

## Apply a union

Once you finish creating your union, select **Apply** to add the union to your workflow. You will see the union node connected to the two unioned datasets in your graph. We named our new union `Union`, and it is a direct output of the original `Correct columns` and `Vendor Cut 2 - demo data` datasets.

![Screenshot of union selection](../../../assets/eff5060f0d060232ef9282290413df2fe7a9b5513b4cf903bef7bb1b1e88bce6.webp)

You can rename or edit the union by selecting the union node and selecting **Edit**.

Drag the white or gray circles on nodes to change connections and remove links on the graph. Select the gray oval on a union node to remove multiple connections.

Remember, a union keeps all rows from both the right and left datasets, including duplicate rows. To remove duplicate rows, add a `Drop duplicates` transform to your union output.

[Learn more about transforms.](../transforms-overview/index.md)