```Python hl_lines="8-13"
{!../../../docs_src/sql_databases/sql_app/tests/test_sql_app.py!}
```

!!! tip
    You could reduce duplication in that code by putting it in a function and using it from both `database.py` and `tests/test_sql_app.py`.

    For simplicity and to focus on the specific testing code, we are just copying it.

## Create the database

### Create the `FastAPI` app

```Python hl_lines="46"
{!../../../docs_src/nosql_databases/tutorial001.py!}
```

### Create the *path operation function*

## Motivation

Let's start with a simple example:

```Python
{!../../../docs_src/python_types/tutorial001.py!}
```

Calling this program outputs:

```
John Doe
```

The function does the following:

* Takes a `first_name` and `last_name`.
* Converts the first letter of each one to upper case with `title()`.

    * PR [#294](https://github.com/tiangolo/fastapi/pull/294).

## 0.28.0

* Implement dependency cache per request.
    * This avoids calling each dependency multiple times for the same request.
    * This is useful while calling external services, performing costly computation, etc.

    But **FastAPI** will know that it has to solve `query_extractor` first, to pass the results of that to `query_or_cookie_extractor` while calling it.

```mermaid
graph TB

query_extractor(["query_extractor"])
query_or_cookie_extractor(["query_or_cookie_extractor"])

read_query["/items/"]

    ```Python hl_lines="5  22"
    {!> ../../../docs_src/encoder/tutorial001.py!}
    ```

In this example, it would convert the Pydantic model to a `dict`, and the `datetime` to a `str`.

The result of calling it is something that can be encoded with the Python standard <a href="https://docs.python.org/3/library/json.html#json.dumps" class="external-link" target="_blank">`json.dumps()`</a>.

!!! tip
    You'll see what other "things", apart from functions, can be used as dependencies in the next chapter.

Whenever a new request arrives, **FastAPI** will take care of:

* Calling your dependency ("dependable") function with the correct parameters.
* Get the result from your function.
* Assign that result to the parameter in your *path operation function*.

```mermaid
graph TB

The idea is for the **FastAPI** community to be kind and welcoming. At the same time, don't accept bullying or disrespectful behavior towards others. We have to take care of each other.

---

Here's how to help others with questions (in discussions or issues):

### Understand the question

{!../../../docs_src/custom_response/tutorial004.py!}
```

In this example, the function `generate_html_response()` already generates and returns a `Response` instead of returning the HTML in a `str`.

By returning the result of calling `generate_html_response()`, you are already returning a `Response` that will override the default **FastAPI** behavior.

Then the cashier 💁 says "I'm finished with doing the burgers" by putting your number on the counter's display, but you don't jump like crazy immediately when the displayed number changes to your turn number. You know no one will steal your burgers because you have the number of your turn, and they have theirs.