# Build Data Table

> `UiPath.Core.Activities.BuildDataTable`

`UiPath.Core.Activities.BuildDataTable`

The **Build Data Table** activity allows you to create and customize a data table within your automation workflow.

## Project compatibility

**Windows** | **Windows - Legacy**

## Using the Build Data Table window

Select the **DataTable** button in the activity body to open the **Build Data Table** window, where you can customize the d.

![The Build Data Table window.](https://dev-assets.cms.uipath.com/assets/images/activities/activities-the-build-data-table-window-179604-26acb94b.webp)

The window initially displays a table with two columns and two rows:

* The first row contains editable values.
* The second row is not removable, but it is not displayed in the output table.

To add a column, select **Add Column**. This opens the **New Column** window, where you can create and customize new columns for your data table.

To modify an existing column, select **Edit Column**.

:::note
Changing the data type of a column erases all data in that column.
:::

  ![docs image](https://dev-assets.cms.uipath.com/assets/images/activities/activities-docs-image-181188-6389e19c.webp)

The **New Column** window contains the following fields:

* **Column Name**—The title of the column. This field supports only strings.
* **Data Type**—The type of values that the new column is going to accept.
* **Allow Null**—If this check box is selected, null values can be added to the rows of this column.
* **Auto Increment**—The check box is displayed only if the **Data Type** is set to Int32. If selected, the value of this column is automatically incremented by 1 every time a new row is added.
* **Default Value**—The default value of all the rows that are to be added to this column.
* **Unique**—If selected, all the rows in this column need to have unique values.
* **Max Length**—The maximum number of characters accepted for this column. Use `-1` for no limit.

## Adding and editing columns

The **Build Data Table** window initially displays a table with two columns and two rows:

* The first row contains editable values.
* The second row is not removable, but it is not displayed in the output table.

To add a column, select **Add Column**. This opens the **New Column** window, where you can create and customize new columns for your data table.

To modify an existing column, select **Edit Column**.

:::note
Changing the data type of a column erases all data in that column.
:::

## New column properties

  ![The New Column window.](https://dev-assets.cms.uipath.com/assets/images/activities/activities-docs-image-181188-6389e19c.webp)

The **New Column** window contains the following fields:

* **Column Name**—The title of the column. This field supports only strings.
* **Data Type**—The type of values that the new column is going to accept.
* **Allow Null**—If this check box is selected, null values can be added to the rows of this column.
* **Auto Increment**—The check box is displayed only if the **Data Type** is set to Int32. If selected, the value of this column is automatically incremented by 1 every time a new row is added.
* **Default Value**—The default value of all the rows that are to be added to this column.
* **Unique**—If selected, all the rows in this column need to have unique values.
* **Max Length**—The maximum number of characters accepted for this column. Use `-1` for no limit.

## Build Data Table properties

#### In the Properties panel, the following options are available:

#### **Options**

* **Display Name**—The display name of the activity.

**Misc**
* **Private**—If selected, the values of variables and arguments are no longer logged at Verbose level.

#### **Output**

* **Data Table**—A DataTable variable that stores the information added in the **Build Data Table** window.

## Example of using the Build Data Table activity

You can see how the **Build Data Table** activity is used in an example that incorporates multiple activities and it is used for managing multiple databases. Refer to the [Build and Filter Data Table](https://docs.uipath.com/activities/other/latest/workflow/build-and-filter-data-table) how-to guide.