You can combine `dataclasses` with other type annotations in many different combinations to form complex data structures.

Check the in-code annotation tips above to see more specific details.

## Learn More { #learn-more }

You can also combine `dataclasses` with other Pydantic models, inherit from them, include them in your own models, etc.

{* ../../docs_src/query_params_str_validations/tutorial005_an_py39.py hl[9] *}

/// note | Hinweis

Ein Defaultwert irgendeines Typs, einschließlich `None`, macht den Parameter optional (nicht erforderlich).

///

## Erforderliche Parameter { #required-parameters }

                stone(philosophers-stone) -->|benötigt| harry-1
            end
        ```
        »»»


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* 📝 Add External Link: 10 Tips for adding SQLAlchemy to FastAPI. PR [#11036](https://github.com/tiangolo/fastapi/pull/11036) by [@Donnype](https://github.com/Donnype).
* 📝 Add External Link: Tips on migrating from Flask to FastAPI and vice-versa. PR [#11029](https://github.com/tiangolo/fastapi/pull/11029) by [@jtemporal](https://github.com/jtemporal).