查询 DynamoDB 表 - Amazon DynamoDB

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查询 DynamoDB 表

您可以使用 AWS Management Console、 AWS CLI或 SDK 对 DynamoDB 表执行查询。 AWS 有关查询的更多信息,请参阅 DynamoDB 中的查询操作

使用 AWS SDK 查询 DynamoDB 表

以下代码示例显示如何使用 AWS SDK 查询 DynamoDB 表。

.NET
AWS SDK for .NET
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库 中查找完整示例,了解如何进行设置和运行。

/// <summary> /// Queries the table for movies released in a particular year and /// then displays the information for the movies returned. /// </summary> /// <param name="client">The initialized DynamoDB client object.</param> /// <param name="tableName">The name of the table to query.</param> /// <param name="year">The release year for which we want to /// view movies.</param> /// <returns>The number of movies that match the query.</returns> public static async Task<int> QueryMoviesAsync(AmazonDynamoDBClient client, string tableName, int year) { var movieTable = Table.LoadTable(client, tableName); var filter = new QueryFilter("year", QueryOperator.Equal, year); Console.WriteLine("\nFind movies released in: {year}:"); var config = new QueryOperationConfig() { Limit = 10, // 10 items per page. Select = SelectValues.SpecificAttributes, AttributesToGet = new List<string> { "title", "year", }, ConsistentRead = true, Filter = filter, }; // Value used to track how many movies match the // supplied criteria. var moviesFound = 0; Search search = movieTable.Query(config); do { var movieList = await search.GetNextSetAsync(); moviesFound += movieList.Count; foreach (var movie in movieList) { DisplayDocument(movie); } } while (!search.IsDone); return moviesFound; }
  • 有关 API 详细信息,请参阅 AWS SDK for .NET API 参考中的 Query

Bash
AWS CLI 使用 Bash 脚本
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

############################################################################# # function dynamodb_query # # This function queries a DynamoDB table. # # Parameters: # -n table_name -- The name of the table. # -k key_condition_expression -- The key condition expression. # -a attribute_names -- Path to JSON file containing the attribute names. # -v attribute_values -- Path to JSON file containing the attribute values. # [-p projection_expression] -- Optional projection expression. # # Returns: # The items as json output. # And: # 0 - If successful. # 1 - If it fails. ########################################################################### function dynamodb_query() { local table_name key_condition_expression attribute_names attribute_values projection_expression response local option OPTARG # Required to use getopts command in a function. # ###################################### # Function usage explanation ####################################### function usage() { echo "function dynamodb_query" echo "Query a DynamoDB table." echo " -n table_name -- The name of the table." echo " -k key_condition_expression -- The key condition expression." echo " -a attribute_names -- Path to JSON file containing the attribute names." echo " -v attribute_values -- Path to JSON file containing the attribute values." echo " [-p projection_expression] -- Optional projection expression." echo "" } while getopts "n:k:a:v:p:h" option; do case "${option}" in n) table_name="${OPTARG}" ;; k) key_condition_expression="${OPTARG}" ;; a) attribute_names="${OPTARG}" ;; v) attribute_values="${OPTARG}" ;; p) projection_expression="${OPTARG}" ;; h) usage return 0 ;; \?) echo "Invalid parameter" usage return 1 ;; esac done export OPTIND=1 if [[ -z "$table_name" ]]; then errecho "ERROR: You must provide a table name with the -n parameter." usage return 1 fi if [[ -z "$key_condition_expression" ]]; then errecho "ERROR: You must provide a key condition expression with the -k parameter." usage return 1 fi if [[ -z "$attribute_names" ]]; then errecho "ERROR: You must provide a attribute names with the -a parameter." usage return 1 fi if [[ -z "$attribute_values" ]]; then errecho "ERROR: You must provide a attribute values with the -v parameter." usage return 1 fi if [[ -z "$projection_expression" ]]; then response=$(aws dynamodb query \ --table-name "$table_name" \ --key-condition-expression "$key_condition_expression" \ --expression-attribute-names file://"$attribute_names" \ --expression-attribute-values file://"$attribute_values") else response=$(aws dynamodb query \ --table-name "$table_name" \ --key-condition-expression "$key_condition_expression" \ --expression-attribute-names file://"$attribute_names" \ --expression-attribute-values file://"$attribute_values" \ --projection-expression "$projection_expression") fi local error_code=${?} if [[ $error_code -ne 0 ]]; then aws_cli_error_log $error_code errecho "ERROR: AWS reports query operation failed.$response" return 1 fi echo "$response" return 0 }

本示例中使用的实用程序函数。

############################################################################### # function errecho # # This function outputs everything sent to it to STDERR (standard error output). ############################################################################### function errecho() { printf "%s\n" "$*" 1>&2 } ############################################################################## # function aws_cli_error_log() # # This function is used to log the error messages from the AWS CLI. # # See https://docs.aws.amazon.com/cli/latest/topic/return-codes.html#cli-aws-help-return-codes. # # The function expects the following argument: # $1 - The error code returned by the AWS CLI. # # Returns: # 0: - Success. # ############################################################################## function aws_cli_error_log() { local err_code=$1 errecho "Error code : $err_code" if [ "$err_code" == 1 ]; then errecho " One or more S3 transfers failed." elif [ "$err_code" == 2 ]; then errecho " Command line failed to parse." elif [ "$err_code" == 130 ]; then errecho " Process received SIGINT." elif [ "$err_code" == 252 ]; then errecho " Command syntax invalid." elif [ "$err_code" == 253 ]; then errecho " The system environment or configuration was invalid." elif [ "$err_code" == 254 ]; then errecho " The service returned an error." elif [ "$err_code" == 255 ]; then errecho " 255 is a catch-all error." fi return 0 }
  • 有关 API 详细信息,请参阅《AWS CLI 命令参考》中的 Query

C++
适用于 C++ 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库 中查找完整示例,了解如何进行设置和运行。

//! Perform a query on an Amazon DynamoDB Table and retrieve items. /*! \sa queryItem() \param tableName: The table name. \param partitionKey: The partition key. \param partitionValue: The value for the partition key. \param projectionExpression: The projections expression, which is ignored if empty. \param clientConfiguration: AWS client configuration. \return bool: Function succeeded. */ /* * The partition key attribute is searched with the specified value. By default, all fields and values * contained in the item are returned. If an optional projection expression is * specified on the command line, only the specified fields and values are * returned. */ bool AwsDoc::DynamoDB::queryItems(const Aws::String &tableName, const Aws::String &partitionKey, const Aws::String &partitionValue, const Aws::String &projectionExpression, const Aws::Client::ClientConfiguration &clientConfiguration) { Aws::DynamoDB::DynamoDBClient dynamoClient(clientConfiguration); Aws::DynamoDB::Model::QueryRequest request; request.SetTableName(tableName); if (!projectionExpression.empty()) { request.SetProjectionExpression(projectionExpression); } // Set query key condition expression. request.SetKeyConditionExpression(partitionKey + "= :valueToMatch"); // Set Expression AttributeValues. Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> attributeValues; attributeValues.emplace(":valueToMatch", partitionValue); request.SetExpressionAttributeValues(attributeValues); bool result = true; // "exclusiveStartKey" is used for pagination. Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue> exclusiveStartKey; do { if (!exclusiveStartKey.empty()) { request.SetExclusiveStartKey(exclusiveStartKey); exclusiveStartKey.clear(); } // Perform Query operation. const Aws::DynamoDB::Model::QueryOutcome &outcome = dynamoClient.Query(request); if (outcome.IsSuccess()) { // Reference the retrieved items. const Aws::Vector<Aws::Map<Aws::String, Aws::DynamoDB::Model::AttributeValue>> &items = outcome.GetResult().GetItems(); if (!items.empty()) { std::cout << "Number of items retrieved from Query: " << items.size() << std::endl; // Iterate each item and print. for (const auto &item: items) { std::cout << "******************************************************" << std::endl; // Output each retrieved field and its value. for (const auto &i: item) std::cout << i.first << ": " << i.second.GetS() << std::endl; } } else { std::cout << "No item found in table: " << tableName << std::endl; } exclusiveStartKey = outcome.GetResult().GetLastEvaluatedKey(); } else { std::cerr << "Failed to Query items: " << outcome.GetError().GetMessage(); result = false; break; } } while (!exclusiveStartKey.empty()); return result; }
  • 有关 API 详细信息,请参阅 AWS SDK for C++ API 参考中的 Query

CLI
AWS CLI

示例 1:查询表

以下 query 示例将查询 MusicCollection 表中的项。该表具有 hash-and-range 主键(ArtistSongTitle),但此查询仅指定哈希键值。它返回名为“No One You Know”的艺术家的歌名。

aws dynamodb query \ --table-name MusicCollection \ --projection-expression "SongTitle" \ --key-condition-expression "Artist = :v1" \ --expression-attribute-values file://expression-attributes.json \ --return-consumed-capacity TOTAL

expression-attributes.json 的内容:

{ ":v1": {"S": "No One You Know"} }

输出:

{ "Items": [ { "SongTitle": { "S": "Call Me Today" }, "SongTitle": { "S": "Scared of My Shadow" } } ], "Count": 2, "ScannedCount": 2, "ConsumedCapacity": { "TableName": "MusicCollection", "CapacityUnits": 0.5 } }

有关更多信息,请参阅《Amazon DynamoDB 开发人员指南》中的使用 DynamoDB 中的查询

示例 2:使用强一致性读取查询表并按降序遍历索引

以下示例将执行与第一个示例相同的查询,但返回结果的顺序相反,并且使用强一致性读取。

aws dynamodb query \ --table-name MusicCollection \ --projection-expression "SongTitle" \ --key-condition-expression "Artist = :v1" \ --expression-attribute-values file://expression-attributes.json \ --consistent-read \ --no-scan-index-forward \ --return-consumed-capacity TOTAL

expression-attributes.json 的内容:

{ ":v1": {"S": "No One You Know"} }

输出:

{ "Items": [ { "SongTitle": { "S": "Scared of My Shadow" } }, { "SongTitle": { "S": "Call Me Today" } } ], "Count": 2, "ScannedCount": 2, "ConsumedCapacity": { "TableName": "MusicCollection", "CapacityUnits": 1.0 } }

有关更多信息,请参阅《Amazon DynamoDB 开发人员指南》中的使用 DynamoDB 中的查询

示例 3:筛选出特定结果

以下示例将查询 MusicCollection,但不包括 AlbumTitle 属性中含特定值的结果。请注意,这不会影响 ScannedCountConsumedCapacity,因为筛选器在读取项之后应用。

aws dynamodb query \ --table-name MusicCollection \ --key-condition-expression "#n1 = :v1" \ --filter-expression "NOT (#n2 IN (:v2, :v3))" \ --expression-attribute-names file://names.json \ --expression-attribute-values file://values.json \ --return-consumed-capacity TOTAL

values.json 的内容:

{ ":v1": {"S": "No One You Know"}, ":v2": {"S": "Blue Sky Blues"}, ":v3": {"S": "Greatest Hits"} }

names.json 的内容:

{ "#n1": "Artist", "#n2": "AlbumTitle" }

输出:

{ "Items": [ { "AlbumTitle": { "S": "Somewhat Famous" }, "Artist": { "S": "No One You Know" }, "SongTitle": { "S": "Call Me Today" } } ], "Count": 1, "ScannedCount": 2, "ConsumedCapacity": { "TableName": "MusicCollection", "CapacityUnits": 0.5 } }

有关更多信息,请参阅《Amazon DynamoDB 开发人员指南》中的使用 DynamoDB 中的查询

示例 4:仅检索项计数

以下示例将检索与查询匹配的项计数,但不检索任何项本身。

aws dynamodb query \ --table-name MusicCollection \ --select COUNT \ --key-condition-expression "Artist = :v1" \ --expression-attribute-values file://expression-attributes.json

expression-attributes.json 的内容:

{ ":v1": {"S": "No One You Know"} }

输出:

{ "Count": 2, "ScannedCount": 2, "ConsumedCapacity": null }

有关更多信息,请参阅《Amazon DynamoDB 开发人员指南》中的使用 DynamoDB 中的查询

示例 5:查询索引

以下示例将查询本地二级索引 AlbumTitleIndex。该查询返回基表中已投影到本地二级索引的所有属性。请注意,查询本地二级索引或全局二级索引时,您还必须使用 table-name 参数提供基表的名称。

aws dynamodb query \ --table-name MusicCollection \ --index-name AlbumTitleIndex \ --key-condition-expression "Artist = :v1" \ --expression-attribute-values file://expression-attributes.json \ --select ALL_PROJECTED_ATTRIBUTES \ --return-consumed-capacity INDEXES

expression-attributes.json 的内容:

{ ":v1": {"S": "No One You Know"} }

输出:

{ "Items": [ { "AlbumTitle": { "S": "Blue Sky Blues" }, "Artist": { "S": "No One You Know" }, "SongTitle": { "S": "Scared of My Shadow" } }, { "AlbumTitle": { "S": "Somewhat Famous" }, "Artist": { "S": "No One You Know" }, "SongTitle": { "S": "Call Me Today" } } ], "Count": 2, "ScannedCount": 2, "ConsumedCapacity": { "TableName": "MusicCollection", "CapacityUnits": 0.5, "Table": { "CapacityUnits": 0.0 }, "LocalSecondaryIndexes": { "AlbumTitleIndex": { "CapacityUnits": 0.5 } } } }

有关更多信息,请参阅《Amazon DynamoDB 开发人员指南》中的使用 DynamoDB 中的查询

  • 有关 API 详细信息,请参阅《AWS CLI 命令参考》中的 Query

Go
适用于 Go V2 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库 中查找完整示例,了解如何进行设置和运行。

// TableBasics encapsulates the Amazon DynamoDB service actions used in the examples. // It contains a DynamoDB service client that is used to act on the specified table. type TableBasics struct { DynamoDbClient *dynamodb.Client TableName string } // Query gets all movies in the DynamoDB table that were released in the specified year. // The function uses the `expression` package to build the key condition expression // that is used in the query. func (basics TableBasics) Query(releaseYear int) ([]Movie, error) { var err error var response *dynamodb.QueryOutput var movies []Movie keyEx := expression.Key("year").Equal(expression.Value(releaseYear)) expr, err := expression.NewBuilder().WithKeyCondition(keyEx).Build() if err != nil { log.Printf("Couldn't build expression for query. Here's why: %v\n", err) } else { queryPaginator := dynamodb.NewQueryPaginator(basics.DynamoDbClient, &dynamodb.QueryInput{ TableName: aws.String(basics.TableName), ExpressionAttributeNames: expr.Names(), ExpressionAttributeValues: expr.Values(), KeyConditionExpression: expr.KeyCondition(), }) for queryPaginator.HasMorePages() { response, err = queryPaginator.NextPage(context.TODO()) if err != nil { log.Printf("Couldn't query for movies released in %v. Here's why: %v\n", releaseYear, err) break } else { var moviePage []Movie err = attributevalue.UnmarshalListOfMaps(response.Items, &moviePage) if err != nil { log.Printf("Couldn't unmarshal query response. Here's why: %v\n", err) break } else { movies = append(movies, moviePage...) } } } } return movies, err } // Movie encapsulates data about a movie. Title and Year are the composite primary key // of the movie in Amazon DynamoDB. Title is the sort key, Year is the partition key, // and Info is additional data. type Movie struct { Title string `dynamodbav:"title"` Year int `dynamodbav:"year"` Info map[string]interface{} `dynamodbav:"info"` } // GetKey returns the composite primary key of the movie in a format that can be // sent to DynamoDB. func (movie Movie) GetKey() map[string]types.AttributeValue { title, err := attributevalue.Marshal(movie.Title) if err != nil { panic(err) } year, err := attributevalue.Marshal(movie.Year) if err != nil { panic(err) } return map[string]types.AttributeValue{"title": title, "year": year} } // String returns the title, year, rating, and plot of a movie, formatted for the example. func (movie Movie) String() string { return fmt.Sprintf("%v\n\tReleased: %v\n\tRating: %v\n\tPlot: %v\n", movie.Title, movie.Year, movie.Info["rating"], movie.Info["plot"]) }
  • 有关 API 详细信息,请参阅 AWS SDK for Go API 参考中的 Query

Java
适用于 Java 2.x 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

使用查询表DynamoDbClient

import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.DynamoDbClient; import software.amazon.awssdk.services.dynamodb.model.AttributeValue; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException; import software.amazon.awssdk.services.dynamodb.model.QueryRequest; import software.amazon.awssdk.services.dynamodb.model.QueryResponse; import java.util.HashMap; /** * Before running this Java V2 code example, set up your development * environment, including your credentials. * * For more information, see the following documentation topic: * * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html * * To query items from an Amazon DynamoDB table using the AWS SDK for Java V2, * its better practice to use the * Enhanced Client. See the EnhancedQueryRecords example. */ public class Query { public static void main(String[] args) { final String usage = """ Usage: <tableName> <partitionKeyName> <partitionKeyVal> Where: tableName - The Amazon DynamoDB table to put the item in (for example, Music3). partitionKeyName - The partition key name of the Amazon DynamoDB table (for example, Artist). partitionKeyVal - The value of the partition key that should match (for example, Famous Band). """; if (args.length != 3) { System.out.println(usage); System.exit(1); } String tableName = args[0]; String partitionKeyName = args[1]; String partitionKeyVal = args[2]; // For more information about an alias, see: // https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/Expressions.ExpressionAttributeNames.html String partitionAlias = "#a"; System.out.format("Querying %s", tableName); System.out.println(""); Region region = Region.US_EAST_1; DynamoDbClient ddb = DynamoDbClient.builder() .region(region) .build(); int count = queryTable(ddb, tableName, partitionKeyName, partitionKeyVal, partitionAlias); System.out.println("There were " + count + " record(s) returned"); ddb.close(); } public static int queryTable(DynamoDbClient ddb, String tableName, String partitionKeyName, String partitionKeyVal, String partitionAlias) { // Set up an alias for the partition key name in case it's a reserved word. HashMap<String, String> attrNameAlias = new HashMap<String, String>(); attrNameAlias.put(partitionAlias, partitionKeyName); // Set up mapping of the partition name with the value. HashMap<String, AttributeValue> attrValues = new HashMap<>(); attrValues.put(":" + partitionKeyName, AttributeValue.builder() .s(partitionKeyVal) .build()); QueryRequest queryReq = QueryRequest.builder() .tableName(tableName) .keyConditionExpression(partitionAlias + " = :" + partitionKeyName) .expressionAttributeNames(attrNameAlias) .expressionAttributeValues(attrValues) .build(); try { QueryResponse response = ddb.query(queryReq); return response.count(); } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); } return -1; } }

使用 DynamoDbClient 和二级索引查询表。

import software.amazon.awssdk.regions.Region; import software.amazon.awssdk.services.dynamodb.DynamoDbClient; import software.amazon.awssdk.services.dynamodb.model.AttributeValue; import software.amazon.awssdk.services.dynamodb.model.DynamoDbException; import software.amazon.awssdk.services.dynamodb.model.QueryRequest; import software.amazon.awssdk.services.dynamodb.model.QueryResponse; import java.util.HashMap; import java.util.Map; /** * Before running this Java V2 code example, set up your development * environment, including your credentials. * * For more information, see the following documentation topic: * * https://docs.aws.amazon.com/sdk-for-java/latest/developer-guide/get-started.html * * Create the Movies table by running the Scenario example and loading the Movie * data from the JSON file. Next create a secondary * index for the Movies table that uses only the year column. Name the index * **year-index**. For more information, see: * * https://docs.aws.amazon.com/amazondynamodb/latest/developerguide/GSI.html */ public class QueryItemsUsingIndex { public static void main(String[] args) { String tableName = "Movies"; Region region = Region.US_EAST_1; DynamoDbClient ddb = DynamoDbClient.builder() .region(region) .build(); queryIndex(ddb, tableName); ddb.close(); } public static void queryIndex(DynamoDbClient ddb, String tableName) { try { Map<String, String> expressionAttributesNames = new HashMap<>(); expressionAttributesNames.put("#year", "year"); Map<String, AttributeValue> expressionAttributeValues = new HashMap<>(); expressionAttributeValues.put(":yearValue", AttributeValue.builder().n("2013").build()); QueryRequest request = QueryRequest.builder() .tableName(tableName) .indexName("year-index") .keyConditionExpression("#year = :yearValue") .expressionAttributeNames(expressionAttributesNames) .expressionAttributeValues(expressionAttributeValues) .build(); System.out.println("=== Movie Titles ==="); QueryResponse response = ddb.query(request); response.items() .forEach(movie -> System.out.println(movie.get("title").s())); } catch (DynamoDbException e) { System.err.println(e.getMessage()); System.exit(1); } } }
  • 有关 API 详细信息,请参阅 AWS SDK for Java 2.x API 参考中的 Query

JavaScript
适用于 JavaScript (v3) 的软件开发工具包
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

此示例使用文档客户端来简化在 DynamoDB 中处理项目的过程。有关 API 的详细信息,请参阅QueryCommand

import { DynamoDBClient } from "@aws-sdk/client-dynamodb"; import { QueryCommand, DynamoDBDocumentClient } from "@aws-sdk/lib-dynamodb"; const client = new DynamoDBClient({}); const docClient = DynamoDBDocumentClient.from(client); export const main = async () => { const command = new QueryCommand({ TableName: "CoffeeCrop", KeyConditionExpression: "OriginCountry = :originCountry AND RoastDate > :roastDate", ExpressionAttributeValues: { ":originCountry": "Ethiopia", ":roastDate": "2023-05-01", }, ConsistentRead: true, }); const response = await docClient.send(command); console.log(response); return response; };
适用于 JavaScript (v2) 的软件开发工具包
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

// Load the AWS SDK for Node.js var AWS = require("aws-sdk"); // Set the region AWS.config.update({ region: "REGION" }); // Create DynamoDB document client var docClient = new AWS.DynamoDB.DocumentClient({ apiVersion: "2012-08-10" }); var params = { ExpressionAttributeValues: { ":s": 2, ":e": 9, ":topic": "PHRASE", }, KeyConditionExpression: "Season = :s and Episode > :e", FilterExpression: "contains (Subtitle, :topic)", TableName: "EPISODES_TABLE", }; docClient.query(params, function (err, data) { if (err) { console.log("Error", err); } else { console.log("Success", data.Items); } });
Kotlin
适用于 Kotlin 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

suspend fun queryDynTable( tableNameVal: String, partitionKeyName: String, partitionKeyVal: String, partitionAlias: String ): Int { val attrNameAlias = mutableMapOf<String, String>() attrNameAlias[partitionAlias] = partitionKeyName // Set up mapping of the partition name with the value. val attrValues = mutableMapOf<String, AttributeValue>() attrValues[":$partitionKeyName"] = AttributeValue.S(partitionKeyVal) val request = QueryRequest { tableName = tableNameVal keyConditionExpression = "$partitionAlias = :$partitionKeyName" expressionAttributeNames = attrNameAlias this.expressionAttributeValues = attrValues } DynamoDbClient { region = "us-east-1" }.use { ddb -> val response = ddb.query(request) return response.count } }
  • 有关 API 详细信息,请参阅《AWS SDK for Kotlin API 参考》中的 Query

PHP
适用于 PHP 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库 中查找完整示例,了解如何进行设置和运行。

$birthKey = [ 'Key' => [ 'year' => [ 'N' => "$birthYear", ], ], ]; $result = $service->query($tableName, $birthKey); public function query(string $tableName, $key) { $expressionAttributeValues = []; $expressionAttributeNames = []; $keyConditionExpression = ""; $index = 1; foreach ($key as $name => $value) { $keyConditionExpression .= "#" . array_key_first($value) . " = :v$index,"; $expressionAttributeNames["#" . array_key_first($value)] = array_key_first($value); $hold = array_pop($value); $expressionAttributeValues[":v$index"] = [ array_key_first($hold) => array_pop($hold), ]; } $keyConditionExpression = substr($keyConditionExpression, 0, -1); $query = [ 'ExpressionAttributeValues' => $expressionAttributeValues, 'ExpressionAttributeNames' => $expressionAttributeNames, 'KeyConditionExpression' => $keyConditionExpression, 'TableName' => $tableName, ]; return $this->dynamoDbClient->query($query); }
  • 有关 API 详细信息,请参阅 AWS SDK for PHP API 参考中的 Query

Python
适用于 Python (Boto3) 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

使用关键条件表达式查询项目。

class Movies: """Encapsulates an Amazon DynamoDB table of movie data.""" def __init__(self, dyn_resource): """ :param dyn_resource: A Boto3 DynamoDB resource. """ self.dyn_resource = dyn_resource # The table variable is set during the scenario in the call to # 'exists' if the table exists. Otherwise, it is set by 'create_table'. self.table = None def query_movies(self, year): """ Queries for movies that were released in the specified year. :param year: The year to query. :return: The list of movies that were released in the specified year. """ try: response = self.table.query(KeyConditionExpression=Key("year").eq(year)) except ClientError as err: logger.error( "Couldn't query for movies released in %s. Here's why: %s: %s", year, err.response["Error"]["Code"], err.response["Error"]["Message"], ) raise else: return response["Items"]

查询项目并将其投影以返回数据的子集。

class UpdateQueryWrapper: def __init__(self, table): self.table = table def query_and_project_movies(self, year, title_bounds): """ Query for movies that were released in a specified year and that have titles that start within a range of letters. A projection expression is used to return a subset of data for each movie. :param year: The release year to query. :param title_bounds: The range of starting letters to query. :return: The list of movies. """ try: response = self.table.query( ProjectionExpression="#yr, title, info.genres, info.actors[0]", ExpressionAttributeNames={"#yr": "year"}, KeyConditionExpression=( Key("year").eq(year) & Key("title").between( title_bounds["first"], title_bounds["second"] ) ), ) except ClientError as err: if err.response["Error"]["Code"] == "ValidationException": logger.warning( "There's a validation error. Here's the message: %s: %s", err.response["Error"]["Code"], err.response["Error"]["Message"], ) else: logger.error( "Couldn't query for movies. Here's why: %s: %s", err.response["Error"]["Code"], err.response["Error"]["Message"], ) raise else: return response["Items"]
  • 有关 API 详细信息,请参阅《AWS SDK for Python (Boto3) API 参考》中的 Query

Ruby
适用于 Ruby 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库 中查找完整示例,了解如何进行设置和运行。

class DynamoDBBasics attr_reader :dynamo_resource attr_reader :table def initialize(table_name) client = Aws::DynamoDB::Client.new(region: "us-east-1") @dynamo_resource = Aws::DynamoDB::Resource.new(client: client) @table = @dynamo_resource.table(table_name) end # Queries for movies that were released in the specified year. # # @param year [Integer] The year to query. # @return [Array] The list of movies that were released in the specified year. def query_items(year) response = @table.query( key_condition_expression: "#yr = :year", expression_attribute_names: {"#yr" => "year"}, expression_attribute_values: {":year" => year}) rescue Aws::DynamoDB::Errors::ServiceError => e puts("Couldn't query for movies released in #{year}. Here's why:") puts("\t#{e.code}: #{e.message}") raise else response.items end
  • 有关 API 详细信息,请参阅 AWS SDK for Ruby API 参考中的 Query

Rust
适用于 Rust 的 SDK
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

查找指定年份制作的电影。

pub async fn movies_in_year( client: &Client, table_name: &str, year: u16, ) -> Result<Vec<Movie>, MovieError> { let results = client .query() .table_name(table_name) .key_condition_expression("#yr = :yyyy") .expression_attribute_names("#yr", "year") .expression_attribute_values(":yyyy", AttributeValue::N(year.to_string())) .send() .await?; if let Some(items) = results.items { let movies = items.iter().map(|v| v.into()).collect(); Ok(movies) } else { Ok(vec![]) } }
  • 有关 API 详细信息,请参阅《AWS SDK for Rust API 参考》中的 Query

SAP ABAP
SDK for SAP ABAP
注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

TRY. " Query movies for a given year . DATA(lt_attributelist) = VALUE /aws1/cl_dynattributevalue=>tt_attributevaluelist( ( NEW /aws1/cl_dynattributevalue( iv_n = |{ iv_year }| ) ) ). DATA(lt_key_conditions) = VALUE /aws1/cl_dyncondition=>tt_keyconditions( ( VALUE /aws1/cl_dyncondition=>ts_keyconditions_maprow( key = 'year' value = NEW /aws1/cl_dyncondition( it_attributevaluelist = lt_attributelist iv_comparisonoperator = |EQ| ) ) ) ). oo_result = lo_dyn->query( iv_tablename = iv_table_name it_keyconditions = lt_key_conditions ). DATA(lt_items) = oo_result->get_items( ). "You can loop over the results to get item attributes. LOOP AT lt_items INTO DATA(lt_item). DATA(lo_title) = lt_item[ key = 'title' ]-value. DATA(lo_year) = lt_item[ key = 'year' ]-value. ENDLOOP. DATA(lv_count) = oo_result->get_count( ). MESSAGE 'Item count is: ' && lv_count TYPE 'I'. CATCH /aws1/cx_dynresourcenotfoundex. MESSAGE 'The table or index does not exist' TYPE 'E'. ENDTRY.
  • 有关 API 详细信息,请参阅《适用于 SAP ABAP 的 AWS SDK API 参考》中的 Query

Swift
SDK for Swift
注意

这是预览版 SDK 的预发布文档。本文档随时可能更改。

注意

还有更多相关信息 GitHub。在 AWS 代码示例存储库中查找完整示例,了解如何进行设置和运行。

/// Get all the movies released in the specified year. /// /// - Parameter year: The release year of the movies to return. /// /// - Returns: An array of `Movie` objects describing each matching movie. /// func getMovies(fromYear year: Int) async throws -> [Movie] { guard let client = self.ddbClient else { throw MoviesError.UninitializedClient } let input = QueryInput( expressionAttributeNames: [ "#y": "year" ], expressionAttributeValues: [ ":y": .n(String(year)) ], keyConditionExpression: "#y = :y", tableName: self.tableName ) let output = try await client.query(input: input) guard let items = output.items else { throw MoviesError.ItemNotFound } // Convert the found movies into `Movie` objects and return an array // of them. var movieList: [Movie] = [] for item in items { let movie = try Movie(withItem: item) movieList.append(movie) } return movieList }
  • 有关 API 详细信息,请参阅《AWS SDK for Swift API 参考》中的 Query

有关更多 DynamoDB 示例,请参阅使用软件开发工具包的 DynamoDB 的代码示例 AWS