# Source: https://huggingface.co/docs/hub/datasets-duckdb.md

# DuckDB

[DuckDB](https://github.com/duckdb/duckdb) is an in-process SQL [OLAP](https://en.wikipedia.org/wiki/Online_analytical_processing) database management system.
You can use the Hugging Face paths (`hf://`) to access data on the Hub:

The [DuckDB CLI](https://duckdb.org/docs/api/cli/overview.html) (Command Line Interface) is a single, dependency-free executable. 
There are also other APIs available for running DuckDB, including Python, C++, Go, Java, Rust, and more. For additional details, visit their [clients](https://duckdb.org/docs/api/overview.html) page.

> [!TIP]
> For installation details, visit the [installation page](https://duckdb.org/docs/installation).

Starting from version `v0.10.3`, the DuckDB CLI includes native support for accessing datasets on the Hugging Face Hub via URLs with the `hf://` scheme. Here are some features you can leverage with this powerful tool:

- Query public datasets and your own gated and private datasets
- Analyze datasets and perform SQL operations
- Combine datasets and export it to different formats
- Conduct vector similarity search on embedding datasets
- Implement full-text search on datasets

For a complete list of DuckDB features, visit the DuckDB [documentation](https://duckdb.org/docs/).

To start the CLI, execute the following command in the installation folder:

```bash
./duckdb
```

## Forging the Hugging Face URL

To access Hugging Face datasets, use the following URL format:

```plaintext
hf://datasets/{my-username}/{my-dataset}/{path_to_file} 
```

- **my-username**, the user or organization of the dataset, e.g. `ibm`
- **my-dataset**, the dataset name, e.g: `duorc`
- **path_to_parquet_file**, the parquet file path which supports glob patterns, e.g `**/*.parquet`, to query all parquet files

> [!TIP]
> You can query auto-converted Parquet files using the @~parquet branch, which corresponds to the `refs/convert/parquet` revision. For more details, refer to the documentation at https://huggingface.co/docs/datasets-server/en/parquet#conversion-to-parquet.
>
> To reference the `refs/convert/parquet` revision of a dataset, use the following syntax:
>
> ```plaintext
> hf://datasets/{my-username}/{my-dataset}@~parquet/{path_to_file} 
> ```
>
> Here is a sample URL following the above syntax:
>
> ```plaintext
> hf://datasets/ibm/duorc@~parquet/ParaphraseRC/test/0000.parquet
> ```

Let's start with a quick demo to query all the rows of a dataset:

```sql
FROM 'hf://datasets/ibm/duorc/ParaphraseRC/*.parquet' LIMIT 3;
```

Or using traditional SQL syntax:

```sql
SELECT * FROM 'hf://datasets/ibm/duorc/ParaphraseRC/*.parquet' LIMIT 3;
```
In the following sections, we will cover more complex operations you can perform with DuckDB on Hugging Face datasets.