For example, if you need to store it in a database.

For that, **FastAPI** provides a `jsonable_encoder()` function.

## Using the `jsonable_encoder`

Let's imagine that you have a database `fake_db` that only receives JSON compatible data.

For example, it doesn't receive `datetime` objects, as those are not compatible with JSON.

!!! tip
    If you want to call `async` functions in your tests apart from sending requests to your FastAPI application (e.g. asynchronous database functions), have a look at the [Async Tests](../advanced/async-tests.md){.internal-link target=_blank} in the advanced tutorial.

## Separating tests

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

* 创建 `DATABASE_URL`
* 创建 `database`

```Python hl_lines="3  9  12"
{!../../../docs_src/async_sql_databases/tutorial001.py!}
```

!!! tip "提示"

    连接 PostgreSQL 等数据库时，需要修改 `DATABASE_URL`。

## 创建表

本例中，使用 Python 文件创建表，但在生产环境中，应使用集成迁移等功能的 Alembic 创建表。

本例在启动 **FastAPI** 应用前，直接执行这些操作。

* 创建 `engine`
* 使用 `metadata` 对象创建所有表

```Python hl_lines="25-28"

* ✍ `DATABASE_URL`.
* ✍ `database` 🎚.

```Python hl_lines="3  9  12"
{!../../../docs_src/async_sql_databases/tutorial001.py!}
```

!!! tip
    🚥 👆 🔗 🎏 💽 (✅ ✳), 👆 🔜 💪 🔀 `DATABASE_URL`.

## ✍ 🏓

👉 💼, 👥 🏗 🏓 🎏 🐍 📁, ✋️ 🏭, 👆 🔜 🎲 💚 ✍ 👫 ⏮️ ⚗, 🛠️ ⏮️ 🛠️, ♒️.

📥, 👉 📄 🔜 🏃 🔗, ▶️️ ⏭ ▶️ 👆 **FastAPI** 🈸.

* ✍ `engine`.
* ✍ 🌐 🏓 ⚪️➡️ `metadata` 🎚.

```Python hl_lines="25-28"

initial_fake_database = {"rick": "Rick Sanchez"}

fake_database = initial_fake_database.copy()

initial_state = {"except": False, "finally": False}

state = initial_state.copy()

app = FastAPI()


async def get_database():
    temp_database = fake_database.copy()
    try:
        yield temp_database
        fake_database.update(temp_database)
    except HTTPException:

from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.pool import StaticPool

from ..database import Base
from ..main import app, get_db

SQLALCHEMY_DATABASE_URL = "sqlite://"

engine = create_engine(
    SQLALCHEMY_DATABASE_URL,
    connect_args={"check_same_thread": False},
    poolclass=StaticPool,
)

This also means that in many cases you can pass the same object you get from a request **directly to the database**, as everything is validated automatically.

The same applies the other way around, in many cases you can just pass the object you get from the database **directly to the client**.

app = FastAPI()


@app.get("/items/")
async def read_items(
    q: Annotated[
        str | None,
        Query(
            title="Query string",
            description="Query string for the items to search in the database that have a good match",
            min_length=3,
        ),
    ] = None,
):
    results = {"items": [{"item_id": "Foo"}, {"item_id": "Bar"}]}
    if q:
        results.update({"q": q})

async def read_items(
    q: Annotated[
        Union[str, None],
        Query(
            alias="item-query",
            title="Query string",
            description="Query string for the items to search in the database that have a good match",
            min_length=3,
            max_length=50,
            pattern="^fixedquery$",
            deprecated=True,
        ),
    ] = None,
):