> ## Documentation Index
> Fetch the complete documentation index at: https://private-7c7dfe99-mintlify-8a08bda2.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

> Documentation for the One format

# One

| Input | Output | Alias |
| ----- | ------ | ----- |
| ✔     | ✗      |       |

<h2 id="description">
  Description
</h2>

The `One` format is a special input format that doesn't read any data from file, and returns only one row with column of type [`UInt8`](/reference/data-types/int-uint), name `dummy` and value `0` (like the `system.one` table).
Can be used with virtual columns `_file/_path`  to list all files without reading actual data.

<h2 id="example-usage">
  Example usage
</h2>

Example:

```sql title="Query" theme={null}
SELECT _file FROM file('path/to/files/data*', One);
```

```text title="Response" theme={null}
┌─_file────┐
│ data.csv │
└──────────┘
┌─_file──────┐
│ data.jsonl │
└────────────┘
┌─_file────┐
│ data.tsv │
└──────────┘
┌─_file────────┐
│ data.parquet │
└──────────────┘
```

<h2 id="format-settings">
  Format settings
</h2>