本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

# \$1replaceRoot
<a name="replaceRoot"></a>

`$replaceRoot` 運算子用來將根文件取代為指定的內嵌文件。當您想要將巢狀文件提升至最上層或重組資料輸出時，此功能非常有用。

**參數**
+ `newRoot`：將取代現有根文件的新根文件。

## 範例 (MongoDB Shell)
<a name="replaceRoot-examples"></a>

此範例說明如何從客戶訂單中擷取運送地址資訊，這對於產生運送標籤或地址清單非常有用。

**建立範例文件**

```
db.orders.insertMany([
  {
    "_id":1, "orderId": "ORD-2024-001", "customerId": "CUST-12345", "orderDate": "2024-01-15", "shippingAddress": { "name": "María García", "street": "123 Main St", "city": "Seattle", "state": "WA", "zipCode": "98101", "country": "USA" },"totalAmount": 149.99 },
  { "_id":2, "orderId": "ORD-2024-002", "customerId": "CUST-67890", "orderDate": "2024-01-16", "shippingAddress": { "name": "Arnav Desai", "street": "456 Oak Ave", "city": "Portland", "state": "OR", "zipCode": "97201", "country": "USA" }, "totalAmount": 89.50 } ])
```

**查詢範例**

```
db.orders.aggregate([
  {
    $replaceRoot: {
      newRoot: "$shippingAddress"
    }
  }
])
```

**輸出**

```
{
    name: 'María García',
    street: '123 Main St',
    city: 'Seattle',
    state: 'WA',
    zipCode: '98101',
    country: 'USA'
  },
  {
    name: 'Arnav Desai',
    street: '456 Oak Ave',
    city: 'Portland',
    state: 'OR',
    zipCode: '97201',
    country: 'USA'
  }
```

## 程式碼範例
<a name="replaceRoot-code"></a>

若要檢視使用 `$replaceRoot`命令的程式碼範例，請選擇您要使用的語言標籤：

------
#### [ Node.js ]

```
const { MongoClient } = require('mongodb');

async function extractShippingAddresses() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
  const db = client.db('test');
  const collection = db.collection('orders');

  const result = await collection.aggregate([
    {
      $replaceRoot: {
        newRoot: "$shippingAddress"
      }
    }
  ]).toArray();

  console.log(result);

  await client.close();
}

extractShippingAddresses();
```

------
#### [ Python ]

```
from pymongo import MongoClient

def extract_shipping_addresses():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
    db = client['test']
    collection = db['orders']

    result = list(collection.aggregate([
        {
            "$replaceRoot": {
                "newRoot": "$shippingAddress"
            }
        }
    ]))

    print(result)

    client.close()

extract_shipping_addresses()
```

------