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。

# \$1set
<a name="set-update"></a>

Amazon DocumentDB 中的`$set`運算子用於更新文件中指定欄位的值。此運算子可讓您新增欄位或修改文件中現有的欄位。它是 MongoDB Java 驅動程式中的基本更新運算子，與 Amazon DocumentDB 相容。

**參數**
+ `field`：要更新的欄位。
+ `value`： 欄位的新值。

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

下列範例示範如何使用 `$set`運算子更新文件中`Item`的欄位。

**建立範例文件**

```
db.example.insert([
  {
    "Item": "Pen",
    "Colors": ["Red", "Green", "Blue", "Black"],
    "Inventory": {
      "OnHand": 244,
      "MinOnHand": 72
    }
  },
  {
    "Item": "Poster Paint",
    "Colors": ["Red", "Green", "Blue", "White"],
    "Inventory": {
      "OnHand": 120,
      "MinOnHand": 36
    }
  }
])
```

**查詢範例**

```
db.example.update(
  { "Item": "Pen" },
  { $set: { "Item": "Gel Pen" } }
)
```

**輸出**

```
{
  "Item": "Gel Pen",
  "Colors": ["Red", "Green", "Blue", "Black"],
  "Inventory": {
    "OnHand": 244,
    "MinOnHand": 72
  }
}
```

## 程式碼範例
<a name="set-code"></a>

若要檢視使用 `$set`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 updateDocument() {
  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('example');

  await collection.updateOne(
    { "Item": "Pen" },
    { $set: { "Item": "Gel Pen" } }
  );

  const updatedDocument = await collection.findOne({ "Item": "Gel Pen" });
  console.log(updatedDocument);

  await client.close();
}

updateDocument();
```

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

```
from pymongo import MongoClient

def update_document():
    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.example

    collection.update_one(
        {"Item": "Pen"},
        {"$set": {"Item": "Gel Pen"}}
    )

    updated_document = collection.find_one({"Item": "Gel Pen"})
    print(updated_document)

    client.close()

update_document()
```

------