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。

# 使用 的 Amazon DynamoDB 範例 適用於 C\$1\$1 的 AWS SDK
<a name="examples-dynamodb"></a>

Amazon DynamoDB 是一項完全受管的 NoSQL 資料庫服務，可提供快速且可預期的效能及無縫的可擴展性。下列範例示範如何使用 編寫 [Amazon DynamoDB](https://aws.amazon.com/dynamodb) 的程式 適用於 C\$1\$1 的 AWS SDK。

**注意**  
本指南僅提供示範特定技術所需的程式碼，但[完整的範例程式碼可在 GitHub 上取得](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp)。在 GitHub 上，您可以下載單一來源檔案，也可以在本機複製儲存庫，以取得、建置和執行所有範例。

**Topics**
+ [在 DynamoDB 中使用資料表](examples-dynamodb-tables.md)
+ [在 DynamoDB 中使用項目](examples-dynamodb-items.md)

# 在 DynamoDB 中使用資料表
<a name="examples-dynamodb-tables"></a>

資料表是 DynamoDB 資料庫中所有項目的容器。您必須先建立資料表，才能從 DynamoDB 新增或移除資料。

對於每個資料表，您必須定義：
+ 您的 AWS 帳戶 和 的唯一資料表*名稱* AWS 區域。
+ 每個值都必須是唯一*的主索引鍵*。資料表中的兩個項目不能具有相同的主索引鍵值。

  主索引鍵可以是*簡單的*，包含單一分割區 (HASH) 索引鍵；也可以是*複合的*，包含分割區和排序 (RANGE) 索引鍵。

  每個索引鍵值都有一個關聯的*資料類型*，由 [ScalarAttributeType](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/namespace_aws_1_1_dynamo_d_b_1_1_model.html#a4b39ae66214e022d3737079d071e4bcb.html) 類別列舉。索引鍵值可以是二進位 (B)、數值 (N)、或字串 (S)。如需詳細資訊，請參閱《Amazon DynamoDB 開發人員指南》中的[命名規則和資料類型](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html)。
+  定義資料表預留讀取/寫入容量單位數量的*佈建輸送量*值。
**注意**  
 [Amazon DynamoDB 定價](https://aws.amazon.com/dynamodb/pricing/)是根據您對資料表設定的佈建輸送量值，所以請只預留您認為您的資料表需要的容量。  
資料表的佈建輸送量可以隨時修改，因此您可以在需要變更時調整容量。

## 建立資料表
<a name="dynamodb-create-table"></a>

使用 [DynamoDB 用戶端](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_dynamo_d_b_client.html)`CreateTable`方法來建立新的 DynamoDB 資料表。您需要建構資料表屬性和資料表結構描述，這兩項都會用來識別資料表的主索引鍵。您也必須提供初始佈建輸送量值和資料表名稱。 `CreateTable` 是非同步操作。 `GetTableStatus`會傳回 CREATING，直到資料表處於 ACTIVE 且可供使用為止。

### 使用簡單主索引鍵建立資料表
<a name="dynamodb-create-table-simple"></a>

此程式碼會使用簡單主索引鍵 ("Name") 來建立資料表。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/AttributeDefinition.h>
#include <aws/dynamodb/model/CreateTableRequest.h>
#include <aws/dynamodb/model/KeySchemaElement.h>
#include <aws/dynamodb/model/ProvisionedThroughput.h>
#include <aws/dynamodb/model/ScalarAttributeType.h>
#include <iostream>
```

 **Code** 

```
//! Create an Amazon DynamoDB table.
/*!
  \sa createTable()
  \param tableName: Name for the DynamoDB table.
  \param primaryKey: Primary key for the DynamoDB table.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */
bool AwsDoc::DynamoDB::createTable(const Aws::String &tableName,
                                   const Aws::String &primaryKey,
                                   const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    std::cout << "Creating table " << tableName <<
              " with a simple primary key: \"" << primaryKey << "\"." << std::endl;

    Aws::DynamoDB::Model::CreateTableRequest request;

    Aws::DynamoDB::Model::AttributeDefinition hashKey;
    hashKey.SetAttributeName(primaryKey);
    hashKey.SetAttributeType(Aws::DynamoDB::Model::ScalarAttributeType::S);
    request.AddAttributeDefinitions(hashKey);

    Aws::DynamoDB::Model::KeySchemaElement keySchemaElement;
    keySchemaElement.WithAttributeName(primaryKey).WithKeyType(
            Aws::DynamoDB::Model::KeyType::HASH);
    request.AddKeySchema(keySchemaElement);

    Aws::DynamoDB::Model::ProvisionedThroughput throughput;
    throughput.WithReadCapacityUnits(5).WithWriteCapacityUnits(5);
    request.SetProvisionedThroughput(throughput);
    request.SetTableName(tableName);

    const Aws::DynamoDB::Model::CreateTableOutcome &outcome = dynamoClient.CreateTable(
            request);
    if (outcome.IsSuccess()) {
        std::cout << "Table \""
                  << outcome.GetResult().GetTableDescription().GetTableName() <<
                  " created!" << std::endl;
    }
    else {
        std::cerr << "Failed to create table: " << outcome.GetError().GetMessage()
                  << std::endl;
        return false;
    }

    return waitTableActive(tableName, dynamoClient);
}
```

請參閱[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/create_table.cpp)。

### 使用複合主索引鍵建立資料表
<a name="dynamodb-create-table-composite"></a>

新增另一個 [AttributeDefinition](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_attribute_definition.html) 和 [KeySchemaElement](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_key_schema_element.html) 到 [CreateTableRequest](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_create_table_request.html)。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/AttributeDefinition.h>
#include <aws/dynamodb/model/CreateTableRequest.h>
#include <aws/dynamodb/model/KeySchemaElement.h>
#include <aws/dynamodb/model/ProvisionedThroughput.h>
#include <aws/dynamodb/model/ScalarAttributeType.h>
#include <iostream>
```

 **Code** 

```
//! Create an Amazon DynamoDB table with a composite key.
/*!
  \sa createTableWithCompositeKey()
  \param tableName: Name for the DynamoDB table.
  \param partitionKey: Name for the partition (hash) key.
  \param sortKey: Name for the sort (range) key.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */
bool AwsDoc::DynamoDB::createTableWithCompositeKey(const Aws::String &tableName,
                                                   const Aws::String &partitionKey,
                                                   const Aws::String &sortKey,
                                                   const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    std::cout << "Creating table " << tableName <<
              " with a composite primary key:\n" \
            "* " << partitionKey << " - partition key\n" \
            "* " << sortKey << " - sort key\n";

    Aws::DynamoDB::Model::CreateTableRequest request;

    Aws::DynamoDB::Model::AttributeDefinition hashKey1, hashKey2;
    hashKey1.WithAttributeName(partitionKey).WithAttributeType(
            Aws::DynamoDB::Model::ScalarAttributeType::S);
    request.AddAttributeDefinitions(hashKey1);
    hashKey2.WithAttributeName(sortKey).WithAttributeType(
            Aws::DynamoDB::Model::ScalarAttributeType::S);
    request.AddAttributeDefinitions(hashKey2);

    Aws::DynamoDB::Model::KeySchemaElement keySchemaElement1, keySchemaElement2;
    keySchemaElement1.WithAttributeName(partitionKey).WithKeyType(
            Aws::DynamoDB::Model::KeyType::HASH);
    request.AddKeySchema(keySchemaElement1);
    keySchemaElement2.WithAttributeName(sortKey).WithKeyType(
            Aws::DynamoDB::Model::KeyType::RANGE);
    request.AddKeySchema(keySchemaElement2);

    Aws::DynamoDB::Model::ProvisionedThroughput throughput;
    throughput.WithReadCapacityUnits(5).WithWriteCapacityUnits(5);
    request.SetProvisionedThroughput(throughput);

    request.SetTableName(tableName);

    const Aws::DynamoDB::Model::CreateTableOutcome &outcome = dynamoClient.CreateTable(
            request);
    if (outcome.IsSuccess()) {
        std::cout << "Table \""
                  << outcome.GetResult().GetTableDescription().GetTableName() <<
                  "\" was created!" << std::endl;
    }
    else {
        std::cerr << "Failed to create table:" << outcome.GetError().GetMessage()
                  << std::endl;
        return false;
    }

    return waitTableActive(tableName, dynamoClient);
}
```

請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/create_table_composite_key.cpp)。

## 列出資料表
<a name="dynamodb-list-tables"></a>

您可以呼叫 [DynamoDB 用戶端](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_dynamo_d_b_client.html)`ListTables`方法，列出特定區域中的資料表。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/core/utils/Outcome.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/ListTablesRequest.h>
#include <aws/dynamodb/model/ListTablesResult.h>
#include <iostream>
```

 **Code** 

```
//! List the Amazon DynamoDB tables for the current AWS account.
/*!
  \sa listTables()
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */

bool AwsDoc::DynamoDB::listTables(
        const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    Aws::DynamoDB::Model::ListTablesRequest listTablesRequest;
    listTablesRequest.SetLimit(50);
    do {
        const Aws::DynamoDB::Model::ListTablesOutcome &outcome = dynamoClient.ListTables(
                listTablesRequest);
        if (!outcome.IsSuccess()) {
            std::cout << "Error: " << outcome.GetError().GetMessage() << std::endl;
            return false;
        }

        for (const auto &tableName: outcome.GetResult().GetTableNames())
            std::cout << tableName << std::endl;
        listTablesRequest.SetExclusiveStartTableName(
                outcome.GetResult().GetLastEvaluatedTableName());

    } while (!listTablesRequest.GetExclusiveStartTableName().empty());

    return true;
}
```

根據預設，每次呼叫最多傳回 100 個資料表。在傳回的 [ListTablesOutcome](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_dynamo_d_b_client.html) 物件`GetExclusiveStartTableName`上使用 ，以取得上次評估的資料表。您可以使用這個值，在前次列表最後傳回值之後開始列表。

請參閱[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/list_tables.cpp)。

## 擷取資料表的相關資訊
<a name="dynamodb-describe-table"></a>

您可以呼叫 [DynamoDB 用戶端](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_dynamo_d_b_client.html)`DescribeTable`方法，進一步了解資料表。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/DescribeTableRequest.h>
#include <iostream>
```

 **Code** 

```
//! Describe an Amazon DynamoDB table.
/*!
  \sa describeTable()
  \param tableName: The DynamoDB table name.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
*/
bool AwsDoc::DynamoDB::describeTable(const Aws::String &tableName,
                                     const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    Aws::DynamoDB::Model::DescribeTableRequest request;
    request.SetTableName(tableName);

    const Aws::DynamoDB::Model::DescribeTableOutcome &outcome = dynamoClient.DescribeTable(
            request);

    if (outcome.IsSuccess()) {
        const Aws::DynamoDB::Model::TableDescription &td = outcome.GetResult().GetTable();
        std::cout << "Table name  : " << td.GetTableName() << std::endl;
        std::cout << "Table ARN   : " << td.GetTableArn() << std::endl;
        std::cout << "Status      : "
                  << Aws::DynamoDB::Model::TableStatusMapper::GetNameForTableStatus(
                          td.GetTableStatus()) << std::endl;
        std::cout << "Item count  : " << td.GetItemCount() << std::endl;
        std::cout << "Size (bytes): " << td.GetTableSizeBytes() << std::endl;

        const Aws::DynamoDB::Model::ProvisionedThroughputDescription &ptd = td.GetProvisionedThroughput();
        std::cout << "Throughput" << std::endl;
        std::cout << "  Read Capacity : " << ptd.GetReadCapacityUnits() << std::endl;
        std::cout << "  Write Capacity: " << ptd.GetWriteCapacityUnits() << std::endl;

        const Aws::Vector<Aws::DynamoDB::Model::AttributeDefinition> &ad = td.GetAttributeDefinitions();
        std::cout << "Attributes" << std::endl;
        for (const auto &a: ad)
            std::cout << "  " << a.GetAttributeName() << " (" <<
                      Aws::DynamoDB::Model::ScalarAttributeTypeMapper::GetNameForScalarAttributeType(
                              a.GetAttributeType()) <<
                      ")" << std::endl;
    }
    else {
        std::cerr << "Failed to describe table: " << outcome.GetError().GetMessage();
    }

    return outcome.IsSuccess();
}
```

請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/describe_table.cpp)。

## 修改資料表
<a name="dynamodb-update-table"></a>

您可以隨時呼叫 [DynamoDB 用戶端](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_dynamo_d_b_client.html)`UpdateTable`方法，修改資料表的佈建輸送量值。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/core/utils/Outcome.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/ProvisionedThroughput.h>
#include <aws/dynamodb/model/UpdateTableRequest.h>
#include <iostream>
```

 **Code** 

```
//! Update a DynamoDB table.
/*!
  \sa updateTable()
  \param tableName: Name for the DynamoDB table.
  \param readCapacity: Provisioned read capacity.
  \param writeCapacity: Provisioned write capacity.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */
bool AwsDoc::DynamoDB::updateTable(const Aws::String &tableName,
                                   long long readCapacity, long long writeCapacity,
                                   const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    std::cout << "Updating " << tableName << " with new provisioned throughput values"
              << std::endl;
    std::cout << "Read capacity : " << readCapacity << std::endl;
    std::cout << "Write capacity: " << writeCapacity << std::endl;

    Aws::DynamoDB::Model::UpdateTableRequest request;
    Aws::DynamoDB::Model::ProvisionedThroughput provisionedThroughput;
    provisionedThroughput.WithReadCapacityUnits(readCapacity).WithWriteCapacityUnits(
            writeCapacity);
    request.WithProvisionedThroughput(provisionedThroughput).WithTableName(tableName);

    const Aws::DynamoDB::Model::UpdateTableOutcome &outcome = dynamoClient.UpdateTable(
            request);
    if (outcome.IsSuccess()) {
        std::cout << "Successfully updated the table." << std::endl;
    } else {
        const Aws::DynamoDB::DynamoDBError &error = outcome.GetError();
        if (error.GetErrorType() == Aws::DynamoDB::DynamoDBErrors::VALIDATION &&
            error.GetMessage().find("The provisioned throughput for the table will not change") != std::string::npos) {
            std::cout << "The provisioned throughput for the table will not change." << std::endl;
        } else {
            std::cerr << outcome.GetError().GetMessage() << std::endl;
            return false;
        }
    }

    return waitTableActive(tableName, dynamoClient);
}
```

請參閱[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/update_table.cpp)。

## 刪除資料表
<a name="dynamodb-delete-table"></a>

呼叫 [DynamoDB 用戶端](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_dynamo_d_b_client.html)`DeleteTable`方法並傳遞資料表的名稱。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/DeleteTableRequest.h>
#include <iostream>
```

 **Code** 

```
//! Delete an Amazon DynamoDB table.
/*!
  \sa deleteTable()
  \param tableName: The DynamoDB table name.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
*/
bool AwsDoc::DynamoDB::deleteTable(const Aws::String &tableName,
                                   const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    Aws::DynamoDB::Model::DeleteTableRequest request;
    request.SetTableName(tableName);

    const Aws::DynamoDB::Model::DeleteTableOutcome &result = dynamoClient.DeleteTable(
            request);
    if (result.IsSuccess()) {
        std::cout << "Your table \""
                  << result.GetResult().GetTableDescription().GetTableName()
                  << " was deleted.\n";
    }
    else {
        std::cerr << "Failed to delete table: " << result.GetError().GetMessage()
                  << std::endl;
    }

    return result.IsSuccess();
}
```

請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/delete_table.cpp)。

## 詳細資訊
<a name="more-info"></a>
+  《Amazon DynamoDB 開發人員指南》中的[使用資料表的指導方針](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GuidelinesForTables.html) 
+  《Amazon[ DynamoDB 開發人員指南》中的使用 DynamoDB 中的資料表](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/WorkingWithTables.html) DynamoDB 

# 在 DynamoDB 中使用項目
<a name="examples-dynamodb-items"></a>

在 DynamoDB 中，項目是*屬性*的集合，每個屬性都有*名稱*和*值*。屬性值可以是純量、集合或文件類型。如需詳細資訊，請參閱《Amazon DynamoDB 開發人員指南》中的[命名規則和資料類型](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/HowItWorks.NamingRulesDataTypes.html)。

## 從資料表擷取項目
<a name="dynamodb-get-item"></a>

呼叫 [DynamoDB 用戶端](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_dynamo_d_b_client.html)`GetItem`方法。傳遞 [GetItemRequest](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_get_item_request.html) 物件，其中包含您想要的項目的資料表名稱和主索引鍵值。它傳回 [GetItemResult](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_get_item_result.html) 物件。

您可以使用傳回`GetItemResult`物件的 `GetItem()`方法，擷取與項目相關聯的`Aws::Map`金鑰`Aws::String`和值 [AttributeValue](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_attribute_value.html) 對的 。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/AttributeDefinition.h>
#include <aws/dynamodb/model/GetItemRequest.h>
#include <iostream>
```

 **Code** 

```
//! Get an item from an Amazon DynamoDB table.
/*!
  \sa getItem()
  \param tableName: The table name.
  \param partitionKey: The partition key.
  \param partitionValue: The value for the partition key.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */

bool AwsDoc::DynamoDB::getItem(const Aws::String &tableName,
                               const Aws::String &partitionKey,
                               const Aws::String &partitionValue,
                               const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);
    Aws::DynamoDB::Model::GetItemRequest request;

    // Set up the request.
    request.SetTableName(tableName);
    request.AddKey(partitionKey,
                   Aws::DynamoDB::Model::AttributeValue().SetS(partitionValue));

    // Retrieve the item's fields and values.
    const Aws::DynamoDB::Model::GetItemOutcome &outcome = dynamoClient.GetItem(request);
    if (outcome.IsSuccess()) {
        // Reference the retrieved fields/values.
        const Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> &item = outcome.GetResult().GetItem();
        if (!item.empty()) {
            // Output each retrieved field and its value.
            for (const auto &i: item)
                std::cout << "Values: " << i.first << ": " << i.second.GetS()
                          << std::endl;
        }
        else {
            std::cout << "No item found with the key " << partitionKey << std::endl;
        }
    }
    else {
        std::cerr << "Failed to get item: " << outcome.GetError().GetMessage();
    }

    return outcome.IsSuccess();
}
```

請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/get_item.cpp)。

## 將項目新增至資料表
<a name="dynamodb-add-item"></a>

建立代表每個項目的索引鍵`Aws::String`和值 [AttributeValue](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_attribute_value.html) 對。這些項目必須包含資料表主索引鍵欄位的值。如果主索引鍵識別的項目已存在，其欄位會透過請求*更新*。使用 `AddItem`方法將它們新增至 [PutItemRequest](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-dynamodb/html/class_aws_1_1_dynamo_d_b_1_1_model_1_1_put_item_request.html)。

 **包括** 

```
#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/AttributeDefinition.h>
#include <aws/dynamodb/model/PutItemRequest.h>
#include <aws/dynamodb/model/PutItemResult.h>
#include <iostream>
```

 **Code** 

```
//! Put an item in an Amazon DynamoDB table.
/*!
  \sa putItem()
  \param tableName: The table name.
  \param artistKey: The artist key. This is the partition key for the table.
  \param artistValue: The artist value.
  \param albumTitleKey: The album title key.
  \param albumTitleValue: The album title value.
  \param awardsKey: The awards key.
  \param awardsValue: The awards value.
  \param songTitleKey: The song title key.
  \param songTitleValue: The song title value.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
 */
bool AwsDoc::DynamoDB::putItem(const Aws::String &tableName,
                               const Aws::String &artistKey,
                               const Aws::String &artistValue,
                               const Aws::String &albumTitleKey,
                               const Aws::String &albumTitleValue,
                               const Aws::String &awardsKey,
                               const Aws::String &awardsValue,
                               const Aws::String &songTitleKey,
                               const Aws::String &songTitleValue,
                               const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    Aws::DynamoDB::Model::PutItemRequest putItemRequest;
    putItemRequest.SetTableName(tableName);

    putItemRequest.AddItem(artistKey, Aws::DynamoDB::Model::AttributeValue().SetS(
            artistValue)); // This is the hash key.
    putItemRequest.AddItem(albumTitleKey, Aws::DynamoDB::Model::AttributeValue().SetS(
            albumTitleValue));
    putItemRequest.AddItem(awardsKey,
                           Aws::DynamoDB::Model::AttributeValue().SetS(awardsValue));
    putItemRequest.AddItem(songTitleKey,
                           Aws::DynamoDB::Model::AttributeValue().SetS(songTitleValue));

    const Aws::DynamoDB::Model::PutItemOutcome outcome = dynamoClient.PutItem(
            putItemRequest);
    if (outcome.IsSuccess()) {
        std::cout << "Successfully added Item!" << std::endl;
    }
    else {
        std::cerr << outcome.GetError().GetMessage() << std::endl;
        return false;
    }

    return waitTableActive(tableName, dynamoClient);
}
```

請參閱 GitHub 上的[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/put_item.cpp)。

## 更新資料表中的現有項目
<a name="dynamodb-update-item"></a>

您可以使用 DynamoDBClient 的 `UpdateItem`方法，提供資料表名稱、主索引鍵值和要更新的欄位及其對應值，來更新已存在於資料表中的項目屬性。

 **匯入** 

```
#include <aws/core/Aws.h>
#include <aws/dynamodb/DynamoDBClient.h>
#include <aws/dynamodb/model/UpdateItemRequest.h>
#include <aws/dynamodb/model/UpdateItemResult.h>
#include <iostream>
```

 **Code** 

```
//! Update an Amazon DynamoDB table item.
/*!
  \sa updateItem()
  \param tableName: The table name.
  \param partitionKey: The partition key.
  \param partitionValue: The value for the partition key.
  \param attributeKey: The key for the attribute to be updated.
  \param attributeValue: The value for the attribute to be updated.
  \param clientConfiguration: AWS client configuration.
  \return bool: Function succeeded.
  */

/*
 *  The example code only sets/updates an attribute value. It processes
 *  the attribute value as a string, even if the value could be interpreted
 *  as a number. Also, the example code does not remove an existing attribute
 *  from the key value.
 */

bool AwsDoc::DynamoDB::updateItem(const Aws::String &tableName,
                                  const Aws::String &partitionKey,
                                  const Aws::String &partitionValue,
                                  const Aws::String &attributeKey,
                                  const Aws::String &attributeValue,
                                  const Aws::Client::ClientConfiguration &clientConfiguration) {
    Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration);

    // *** Define UpdateItem request arguments.
    // Define TableName argument.
    Aws::DynamoDB::Model::UpdateItemRequest request;
    request.SetTableName(tableName);

    // Define KeyName argument.
    Aws::DynamoDB::Model::AttributeValue attribValue;
    attribValue.SetS(partitionValue);
    request.AddKey(partitionKey, attribValue);

    // Construct the SET update expression argument.
    Aws::String update_expression("SET #a = :valueA");
    request.SetUpdateExpression(update_expression);

    // Construct attribute name argument.
    Aws::Map<Aws::String, Aws::String> expressionAttributeNames;
    expressionAttributeNames["#a"] = attributeKey;
    request.SetExpressionAttributeNames(expressionAttributeNames);

    // Construct attribute value argument.
    Aws::DynamoDB::Model::AttributeValue attributeUpdatedValue;
    attributeUpdatedValue.SetS(attributeValue);
    Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> expressionAttributeValues;
    expressionAttributeValues[":valueA"] = attributeUpdatedValue;
    request.SetExpressionAttributeValues(expressionAttributeValues);

    // Update the item.
    const Aws::DynamoDB::Model::UpdateItemOutcome &outcome = dynamoClient.UpdateItem(
            request);
    if (outcome.IsSuccess()) {
        std::cout << "Item was updated" << std::endl;
    } else {
        std::cerr << outcome.GetError().GetMessage() << std::endl;
        return false;
    }

    return waitTableActive(tableName, dynamoClient);
}
```

請參閱[完整範例](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/dynamodb/update_item.cpp)。

## 詳細資訊
<a name="more-info"></a>
+  《Amazon DynamoDB 開發人員指南》中的[使用項目的指導方針](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GuidelinesForItems.html) 
+  《Amazon[ DynamoDB 開發人員指南》中的使用 DynamoDB 中的項目](https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/WorkingWithItems.html) DynamoDB