## 主**FastAPI**应用程序

现在在`sql_app/main.py`文件中 让我们集成和使用我们之前创建的所有其他部分。

### 创建数据库表

以非常简单的方式创建数据库表：

=== "Python 3.9+"

    ```Python hl_lines="7"
    {!> ../../../docs_src/sql_databases/sql_app_py39/main.py!}
    ```

=== "Python 3.8+"

    ```Python hl_lines="9"
    {!> ../../../docs_src/sql_databases/sql_app/main.py!}
    ```

#### Alembic 注意

* `main`: plik `main.py` ("moduł" w Pythonie).
* `app`: obiekt stworzony w `main.py` w lini `app = FastAPI()`.
* `--reload`: spraw by serwer resetował się po każdej zmianie w kodzie. Używaj tego tylko w środowisku deweloperskim.

</details>

### Wypróbuj

Otwórz link <a href="http://127.0.0.1:8000/items/5?q=somequery" class="external-link" target="_blank">http://127.0.0.1:8000/items/5?q=somequery</a> w przeglądarce.

* `main`: файл `main.py` (модуль Python).
* `app`: объект, созданный внутри `main.py` с помощью строки `app = FastAPI()`.
* `--reload`: перезапуск сервера после изменения кода. Делайте это только во время разработки.

</details>

### Проверка

Откройте браузер на <a href="http://127.0.0.1:8000/items/5?q=somequery" class="external-link" target="_blank">http://127.0.0.1:8000/items/5?q=somequery</a>.

```

</div>

<details markdown="1">
<summary>Informazioni sul comando <code>uvicorn main:app --reload</code>...</summary>

Vediamo il comando `uvicorn main:app` in dettaglio:

* `main`: il file `main.py` (il "modulo" Python).
* `app`: l'oggetto creato dentro `main.py` con la riga di codice `app = FastAPI()`.

* `main`：`main.py` 文件（一个 Python "模块"）。
* `app`：在 `main.py` 文件中通过 `app = FastAPI()` 创建的对象。
* `--reload`：让服务器在更新代码后重新启动。仅在开发时使用该选项。

</details>

### 检查

使用浏览器访问 <a href="http://127.0.0.1:8000/items/5?q=somequery" class="external-link" target="_blank">http://127.0.0.1:8000/items/5?q=somequery</a>。

你将会看到如下 JSON 响应：

```JSON
{"item_id": 5, "q": "somequery"}
```

你已经创建了一个具有以下功能的 API：

It's relatively tightly coupled with relational databases (like MySQL or PostgreSQL), so, having a NoSQL database (like Couchbase, MongoDB, Cassandra, etc) as the main store engine is not very easy.

            ]
        }
    )


def test_main_depends_q_foo():
    response = client.get("/main-depends/?q=foo")
    assert response.status_code == 200
    assert response.json() == {
        "in": "main-depends",
        "params": {"q": "foo", "skip": 0, "limit": 100},
    }


def test_main_depends_q_foo_skip_100_limit_200():
    response = client.get("/main-depends/?q=foo&skip=100&limit=200")

## The main `FastAPI`

Now, let's see the module at `app/main.py`.

Here's where you import and use the class `FastAPI`.

This will be the main file in your application that ties everything together.

And as most of your logic will now live in its own specific module, the main file will be quite simple.

### Import `FastAPI`

### Providing the `root_path`

To achieve this, you can use the command line option `--root-path` like:

<div class="termy">

```console
$ fastapi run main.py --root-path /api/v1

<span style="color: green;">INFO</span>:     Uvicorn running on http://127.0.0.1:8000 (Press CTRL+C to quit)
```

</div>

If you use Hypercorn, it also has the option `--root-path`.

因此，为了能够在同一个文件中使用它们，我们直接导入子模块：

```Python hl_lines="5" title="app/main.py"
{!../../../docs_src/bigger_applications/app/main.py!}
```

### 包含 `users` 和 `items` 的 `APIRouter`

现在，让我们来包含来自 `users` 和 `items` 子模块的 `router`。

```Python hl_lines="10-11" title="app/main.py"
{!../../../docs_src/bigger_applications/app/main.py!}
```

!!! info