> For the complete documentation index, see [llms.txt](https://docs.dataspace.ch/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.dataspace.ch/platform/transformation/preview.md).

# Preview

The preview panel allows previewing the data (max 200 rows), sorting by column, and performing filters.

Once a Transformation has been successfully built, the data is stored in a `.parquet` file and can be efficiently queried and previewed.

By clicking on the details button next to the column names, a statistics panel will open up, giving an overview and some metadata about said column, such as:

* Distinct Count
* Null Count
* Min/Max values

<figure><picture><source srcset="/files/Tn4uKHh4jo84ezcKiy5L" media="(prefers-color-scheme: dark)"><img src="/files/71gaH8fJcjyrF4HhgvIU" alt="Data Preview Statistics"></picture><figcaption></figcaption></figure>

The panel also shows a breakdown of unique values and their frequency and gives the possibility to search by value.

### Custom Filter

The filter input at the top of the preview panel allows SQL-style `WHERE` clause to be applied.

Following is an example filter:

```
"Airline" = 'Air France' AND "To" = 'JFK'
```

### Data Extract

The generated dataset can be extracted as a CSV or Parquet file using the export buttons at the bottom of the table.

{% hint style="info" %}
Please note that the [EXPORTER](file:///5959076/user-roles.md#exporter) role is required to be able to extract data
{% endhint %}