# Query Parameter Models

If you have a group of **query parameters** that are related, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

## Query Parameters with a Pydantic Model

Wenn im Request ein Query-Parameter enthalten war, wird dieser in einem Hintergrundtask in das Log geschrieben.

Und dann schreibt ein weiterer Hintergrundtask, der in der *Pfadoperation-Funktion* erstellt wird, eine Nachricht unter Verwendung des Pfad-Parameters `email`.

## Technische Details

# Body - Multiple Parameters

Now that we have seen how to use `Path` and `Query`, let's see more advanced uses of request body declarations.

## Mix `Path`, `Query` and body parameters

First, of course, you can mix `Path`, `Query` and request body parameter declarations freely and **FastAPI** will know what to do.

And you can also declare body parameters as optional, by setting the default to `None`:

//// tab | Python 3.10+

  /** True if the agreed upon extension parameters includes "client_no_context_takeover". */
  @JvmField val clientNoContextTakeover: Boolean = false,
  /** Should be a value in [8..15]. Any value in that range is acceptable by OkHttp. */
  @JvmField val serverMaxWindowBits: Int? = null,
  /** True if the agreed upon extension parameters includes "server_no_context_takeover". */

```

as it will use that `None` as the default value, and that way make the parameter **not required**.

The `Union[str, None]` part allows your editor to provide better support, but it is not what tells FastAPI that this parameter is not required.

///

Then, we can pass more parameters to `Query`. In this case, the `max_length` parameter that applies to strings:

```Python

{!> ../../docs_src/query_params/tutorial002.py!}
```

////

In this case, the function parameter `q` will be optional, and will be `None` by default.

/// check

Also notice that **FastAPI** is smart enough to notice that the path parameter `item_id` is a path parameter and `q` is not, so, it's a query parameter.

///

## Query parameter type conversion

You can also declare `bool` types, and they will be converted:

{!> ../../docs_src/body/tutorial002_py310.py!}

## Request body + path parameters

You can declare path parameters and request body at the same time.

**FastAPI** will recognize that the function parameters that match path parameters should be **taken from the path**, and that function parameters that are declared to be Pydantic models should be **taken from the request body**.

        router_sig = inspect.signature(router_method)
        app_sig = inspect.signature(app_method)
        param: inspect.Parameter
        for key, param in base_sig.parameters.items():
            router_param: inspect.Parameter = router_sig.parameters[key]
            app_param: inspect.Parameter = app_sig.parameters[key]
            assert param.annotation == router_param.annotation
            assert param.annotation == app_param.annotation

     * <pre>
     * message: {item} is numeric value out of bounds (&lt;{integer} digits&gt;.&lt;{fraction} digits&gt; expected).
     * </pre>
     * @param property The property name for the message. (NotNull)
     * @param fraction The parameter fraction for message. (NotNull)
     * @param integer The parameter integer for message. (NotNull)
     * @return this. (NotNull)

   * parameters.
   */
  public MediaType withoutParameters() {
    return parameters.isEmpty() ? this : create(type, subtype);
  }

  /**
   * Replaces all parameters with the given parameters.
   *
   * @throws IllegalArgumentException if any parameter or value is invalid
   */