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

Amazon DocumentDB 中的`$year`运算符从日期或时间戳中提取年份部分。

**参数**
+ `expression`：要从中提取年份部分的日期或时间戳表达式。

## 示例（MongoDB 外壳）
<a name="year-examples"></a>

以下示例演示如何使用`$year`运算符从日期字段中提取年份部分。

**创建示例文档**

```
db.events.insertMany([
  { "_id": 1, "date": ISODate("2023-04-15T00:00:00Z") },
  { "_id": 3, "date": ISODate("2021-12-31T00:00:00Z") }
]);
```

**查询示例**

```
db.events.aggregate([
  { $project: { year: { $year: "$date" } } }
]);
```

**输出**

```
[
  { "_id": 1, "year": 2023 },
  { "_id": 3, "year": 2021 }
]
```

## 代码示例
<a name="year-code"></a>

要查看使用该`$year`命令的代码示例，请选择要使用的语言的选项卡：

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

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

async function example() {
  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('events');

  const result = await collection.aggregate([
    { $project: { year: { $year: "$date" } } }
  ]).toArray();

  console.log(result);

  await client.close();
}

example();
```

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

```
from pymongo import MongoClient

def example():
    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['events']

    result = list(collection.aggregate([
        {'$project': {'year': {'$year': '$date'}}}
    ]))

    print(result)

    client.close()

example()
```

------