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。

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

Amazon DocumentDB 中的`$sum`運算子會傳回群組中每個文件的指定表達式總和。這是一個群組累積器運算子，通常用於彙總管道的 \$1group 階段，以執行總和計算。

**參數**
+ `expression`：要加總的數值表達式。這可以是欄位路徑、表達式或常數。

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

下列範例示範如何使用 `$sum`運算子來計算每個產品的總銷售額。

**建立範例文件**

```
db.sales.insertMany([
  { product: "abc", price: 10, quantity: 2 },
  { product: "abc", price: 10, quantity: 3 },
  { product: "xyz", price: 20, quantity: 1 },
  { product: "xyz", price: 20, quantity: 5 }
]);
```

**查詢範例**

```
db.sales.aggregate([
  { $group: {
      _id: "$product",
      totalSales: { $sum: { $multiply: [ "$price", "$quantity" ] } }
    }}
]);
```

**輸出**

```
[
  { "_id": "abc", "totalSales": 50 },
  { "_id": "xyz", "totalSales": 120 }
]
```

## 程式碼範例
<a name="sum-code"></a>

若要檢視使用 `$sum`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 example() {
  const uri = 'mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false';
  const client = new MongoClient(uri);

  try {
    await client.connect();

    const db = client.db('test');
    const collection = db.collection('sales');

    const result = await collection.aggregate([
      { $group: {
          _id: "$product",
          totalSales: { $sum: { $multiply: [ "$price", "$quantity" ] } }
        }}
    ]).toArray();

    console.log(result);

  } catch (error) {
    console.error('Error:', error);
  } finally {
    await client.close();
  }
}

example();
```

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

```
from pymongo import MongoClient
from pprint import pprint

def example():
    client = None
    try:
        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.sales

        result = list(collection.aggregate([
            { '$group': {
                '_id': '$product',
                'totalSales': { '$sum': { '$multiply': [ '$price', '$quantity' ] } }
            }}
        ]))

        pprint(result)

    except Exception as e:
        print(f"An error occurred: {e}")

    finally:
        if client:
            client.close()

example()
```

------