---> 100%
```

</div>

## 创建 SQLAlchemy 部件

让我们转到文件`sql_app/database.py`。

### 导入 SQLAlchemy 部件

```Python hl_lines="1-3"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

### 为 SQLAlchemy 定义数据库 URL地址

```Python hl_lines="5-6"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

在这个例子中，我们正在“连接”到一个 SQLite 数据库（用 SQLite 数据库打开一个文件）。

$ pip install sqlalchemy

---> 100%
```

</div>

## ✍ 🇸🇲 🍕

➡️ 🔗 📁 `sql_app/database.py`.

### 🗄 🇸🇲 🍕

```Python hl_lines="1-3"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

### ✍ 💽 📛 🇸🇲

```Python hl_lines="5-6"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

👉 🖼, 👥 "🔗" 🗄 💽 (📂 📁 ⏮️ 🗄 💽).

📁 🔜 🔎 🎏 📁 📁 `sql_app.db`.

    So, you would be able to, for example, share the same data from a Django application in a database with a FastAPI application. Or gradually migrate a Django application using the same database.

    And your users would be able to login from your Django app or from your **FastAPI** app, at the same time.

## Hash and verify the passwords

It's the most popular Python framework and is widely trusted. It is used to build systems like Instagram.

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.

For example, you could want to **return a dictionary** or a database object, but **declare it as a Pydantic model**. This way the Pydantic model would do all the data documentation, validation, etc. for the object that you returned (e.g. a dictionary or database object).

Let's refer to the file `sql_app/database.py`.

### Import the SQLAlchemy parts

```Python hl_lines="1-3"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

### Create a database URL for SQLAlchemy

```Python hl_lines="5-6"
{!../../../docs_src/sql_databases/sql_app/database.py!}
```

In this example, we are "connecting" to a SQLite database (opening a file with the SQLite database).

* `sql_app/__init__.py`: is an empty file.

* `sql_app/database.py`:

```Python
{!../../../docs_src/sql_databases_peewee/sql_app/database.py!}
```

* `sql_app/models.py`:

```Python
{!../../../docs_src/sql_databases_peewee/sql_app/models.py!}
```

* `sql_app/schemas.py`:

```Python
{!../../../docs_src/sql_databases_peewee/sql_app/schemas.py!}
```

* `sql_app/crud.py`:

`sql_app` 🔜 ✔️ 📄 📁:

* `sql_app/__init__.py`: 🛁 📁.

* `sql_app/database.py`:

```Python
{!../../../docs_src/sql_databases_peewee/sql_app/database.py!}
```

* `sql_app/models.py`:

```Python
{!../../../docs_src/sql_databases_peewee/sql_app/models.py!}
```

* `sql_app/schemas.py`:

```Python
{!../../../docs_src/sql_databases_peewee/sql_app/schemas.py!}
```

* `sql_app/crud.py`:

To achieve this, you will normally have a **separate program** that would make sure your application is run on startup. And in many cases, it would also make sure other components or applications are also run, for example, a database.

### Example Tools to Run at Startup

Some examples of the tools that can do this job are:

* Docker
* Kubernetes
* Docker Compose
* Docker in Swarm Mode
* Systemd
* Supervisor

use internally only data that doesn't depend on the resources of dependencies with `yield`.

For example, instead of using the same database session, you would create a new database session inside of the background task, and you would obtain the objects from the database using this new session. And then instead of passing the object from the database as a parameter to the background task function, you would pass the ID of that object and then obtain the object again inside the background...