user = db.query(User).first()
```

然后我们应该声明*路径操作函数*和不带 的依赖关系`async def`，只需使用普通的`def`，如下：

```Python hl_lines="2"
@app.get("/users/{user_id}", response_model=schemas.User)
def read_user(user_id: int, db: Session = Depends(get_db)):
    db_user = crud.get_user(db, user_id=user_id)
    ...
```

!!! info
    如果您需要异步连接到关系数据库，请参阅[Async SQL (Relational) Databases](https://fastapi.tiangolo.com/zh/advanced/async-sql-databases/)

```

⤴️ 👥 🔜 📣 *➡ 🛠️ 🔢* & 🔗 🍵 `async def`, ⏮️ 😐 `def`,:

```Python hl_lines="2"
@app.get("/users/{user_id}", response_model=schemas.User)
def read_user(user_id: int, db: Session = Depends(get_db)):
    db_user = crud.get_user(db, user_id=user_id)
    ...
```

!!! info
    🚥 👆 💪 🔗 👆 🔗 💽 🔁, 👀 [🔁 🗄 (🔗) 💽](../advanced/async-sql-databases.md){.internal-link target=_blank}.

```Python hl_lines="2"
@app.get("/users/{user_id}", response_model=schemas.User)
def read_user(user_id: int, db: Session = Depends(get_db)):
    db_user = crud.get_user(db, user_id=user_id)
    ...
```

!!! info