**FastAPI** doesn't require you to use a SQL (relational) database.

But you can use any relational database that you want.

Here we'll see an example using <a href="https://www.sqlalchemy.org/" class="external-link" target="_blank">SQLAlchemy</a>.

    ```

!!! note
    A path parameter is always required as it has to be part of the path.

    So, you should declare it with `...` to mark it as required.

    Nevertheless, even if you declared it with `None` or set a default value, it would not affect anything, it would still be always required.

## Order the parameters as you need

!!! tip

    {!> ../../../docs_src/settings/app02/main.py!}
    ```

!!! tip
    We'll discuss the `@lru_cache` in a bit.

    For now you can assume `get_settings()` is a normal function.

And then we can require it from the *path operation function* as a dependency and use it anywhere we need it.

=== "Python 3.9+"

    ```Python hl_lines="17  19-21"
    {!> ../../../docs_src/settings/app02_an_py39/main.py!}
    ```

---

Common examples of CPU bound operations are things that require complex math processing.

For example:

* **Audio** or **image processing**.
* **Computer vision**: an image is composed of millions of pixels, each pixel has 3 values / colors, processing that normally requires computing something on those pixels, all at the same time.

They tend to require more complex configurations, a message/job queue manager, like RabbitMQ or Redis, but they allow you to run background tasks in multiple processes, and especially, in multiple servers.

def test_union_scalar_list():
    # For coverage
    # TODO: there might not be a current valid code path that uses this, it would
    # potentially enable query parameters defined as both a scalar and a list
    # but that would require more refactors, also not sure it's really useful
    from fastapi._compat import is_pv1_scalar_field

    field_info = FieldInfo()
    field = ModelField(
        name="foo",
        field_info=field_info,

    return values, errors


async def request_body_to_args(
    required_params: List[ModelField],
    received_body: Optional[Union[Dict[str, Any], FormData]],
) -> Tuple[Dict[str, Any], List[Dict[str, Any]]]:
    values = {}
    errors: List[Dict[str, Any]] = []
    if required_params:
        field = required_params[0]
        field_info = field.field_info
        embed = getattr(field_info, "embed", None)

                    "type": "missing",
                    "loc": ["body", "file"],
                    "msg": "Field required",
                    "input": None,
                },
                {
                    "type": "missing",
                    "loc": ["body", "fileb"],
                    "msg": "Field required",
                    "input": None,
                },
                {
                    "type": "missing",

                    },
                }
            },
            "/required": {
                "get": {
                    "summary": "Required",
                    "operationId": "required_required_get",
                    "parameters": [
                        {
                            "required": True,
                            "schema": {
                                "title": "Foo",

needs_py39 = pytest.mark.skipif(sys.version_info < (3, 9), reason="requires python3.9+")
needs_py310 = pytest.mark.skipif(
    sys.version_info < (3, 10), reason="requires python3.10+"
)
needs_pydanticv2 = pytest.mark.skipif(not PYDANTIC_V2, reason="requires Pydantic v2")