Затем мы создадим объявленную (`Annotated`) зависимость `SessionDep`. Мы сделаем это для того, чтобы упростить остальной код, который будет использовать эту зависимость.

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[25:30]  hl[25:27,30] *}

We will create a FastAPI **dependency** with `yield` that will provide a new `Session` for each request. This is what ensures that we use a single session per request. 🤓

Then we create an `Annotated` dependency `SessionDep` to simplify the rest of the code that will use this dependency.

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[25:30]  hl[25:27,30] *}

Crearemos una **dependencia de FastAPI** con `yield` que proporcionará una nueva `Session` para cada request. Esto es lo que asegura que usemos una sola session por request. 🤓

Luego creamos una dependencia `Annotated` `SessionDep` para simplificar el resto del código que usará esta dependencia.

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[25:30]  hl[25:27,30] *}

### Crear Tablas de Base de Datos al Arrancar

/**
 * A test utility that verifies that your methods and constructors throw {@link
 * NullPointerException} or {@link UnsupportedOperationException} whenever null is passed to a
 * parameter whose declaration or type isn't annotated with an annotation with the simple name
 * {@code Nullable}, {@code CheckForNull}, {@code NullableType}, or {@code NullableDecl}.
 *

{!> ../../docs_src/bigger_applications/app_an/dependencies.py!}
```

////

//// tab | Python 3.8+ nicht annotiert

/// tip | Tipp

Bevorzugen Sie die `Annotated`-Version, falls möglich.

///

```Python hl_lines="1  4-6" title="app/dependencies.py"
{!> ../../docs_src/bigger_applications/app/dependencies.py!}
```

////

/// tip | Tipp

 *  **OkHttp now uses `@Nullable` to annotate all possibly-null values.** We've
    added a compile-time dependency on the JSR 305 annotations. This is a
    [provided][maven_provided] dependency and does not need to be included in
    your build configuration, `.jar` file, or `.apk`. We use
    `@ParametersAreNonnullByDefault` and all parameters and return types are
    never null unless explicitly annotated `@Nullable`.

* In-process background tasks.
* Startup and shutdown events.
* Test client built on HTTPX.
* CORS, GZip, Static Files, Streaming responses.
* Session and Cookie support.
* 100% test coverage.
* 100% type annotated codebase.
* Few hard dependencies.

Starlette is currently the fastest Python framework tested. Only surpassed by Uvicorn, which is not a framework, but a server.

**`Session`**은 **메모리에 객체**를 저장하고 데이터에 필요한 모든 변경 사항을 추적한 후, **`engine`을 통해** 데이터베이스와 통신합니다.

`yield`를 사용해 FastAPI의 **의존성**을 생성하여 각 요청마다 새로운 `Session`을 제공합니다. 이는 요청당 하나의 세션만 사용되도록 보장합니다. 🤓

그런 다음 이 의존성을 사용하는 코드를 간소화하기 위해 `Annotated` 의존성 `SessionDep`을 생성합니다.

{* ../../docs_src/sql_databases/tutorial001_an_py310.py ln[25:30]  hl[25:27,30] *}

### 시작 시 데이터베이스 테이블 생성하기

애플리케이션 시작 시 데이터베이스 테이블을 생성합니다.

  /*
   * Preconditions.checkNotNull is *intended* for performing eager null checks on parameters that a
   * nullness checker can already "prove" are non-null. That means that the first parameter to
   * checkNotNull *should* be annotated to require it to be non-null.
   *
   * However, for a variety of reasons, Google developers have written a ton of code over the past

- Stopped expanding PVCs annotated with node-expand-not-required. ([#131907](https://github.com/kubernetes/kubernetes/pull/131907), [@gnufied](https://github.com/gnufied)) [SIG API Machinery, Etcd, Node, Storage and Testing]