Step 5: Query data in a DynamoDB table

        /// <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;
        }

#############################################################################
# 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
}

The utility functions used in this example.

###############################################################################
# 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
}

//! 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;
}

Example 1: To query a table

The following query example queries items in the MusicCollection table. The table has a hash-and-range primary key (Artist and SongTitle), but this query only specifies the hash key value. It returns song titles by the artist named "No One You Know".

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

Contents of expression-attributes.json:

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

Output:

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

For more information, see Working with Queries in DynamoDB in the Amazon DynamoDB Developer Guide.

Example 2: To query a table using strongly consistent reads and traverse the index in descending order

The following example performs the same query as the first example, but returns results in reverse order and uses strongly consistent reads.

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

Contents of expression-attributes.json:

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

Output:

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

For more information, see Working with Queries in DynamoDB in the Amazon DynamoDB Developer Guide.

Example 3: To filter out specific results

The following example queries the MusicCollection but excludes results with specific values in the AlbumTitle attribute. Note that this does not affect the ScannedCount or ConsumedCapacity, because the filter is applied after the items have been read.

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

Contents of values.json:

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

Contents of names.json:

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

Output:

{
    "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
    }
}

For more information, see Working with Queries in DynamoDB in the Amazon DynamoDB Developer Guide.

Example 4: To retrieve only an item count

The following example retrieves a count of items matching the query, but does not retrieve any of the items themselves.

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

Contents of expression-attributes.json:

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

Output:

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

For more information, see Working with Queries in DynamoDB in the Amazon DynamoDB Developer Guide.

Example 5: To query an index

The following example queries the local secondary index AlbumTitleIndex. The query returns all attributes from the base table that have been projected into the local secondary index. Note that when querying a local secondary index or global secondary index, you must also provide the name of the base table using the table-name parameter.

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

Contents of expression-attributes.json:

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

Output:

{
    "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
            }
        }
    }
}

For more information, see Working with Queries in DynamoDB in the Amazon DynamoDB Developer Guide.

import (
	"context"
	"errors"
	"log"
	"time"

	"github.com/aws/aws-sdk-go-v2/aws"
	"github.com/aws/aws-sdk-go-v2/feature/dynamodb/attributevalue"
	"github.com/aws/aws-sdk-go-v2/feature/dynamodb/expression"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
)

// 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(ctx context.Context, 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(ctx)
			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
}

Define a Movie struct that is used in this example.

import (
	"archive/zip"
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"log"
	"net/http"

	"github.com/aws/aws-sdk-go-v2/feature/dynamodb/attributevalue"
	"github.com/aws/aws-sdk-go-v2/service/dynamodb/types"
)

// 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"])
}

Queries a table by using 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;
    }
}

Queries a table by using DynamoDbClient and a secondary index.

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);
        }
    }
}

This example uses the document client to simplify working with items in DynamoDB. For API details see 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;
};

// 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);
  }
});

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
    }
}

        $birthKey = [
            'Key' => [
                'year' => [
                    'N' => "$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);
    }

Example 1: Invokes a query that returns DynamoDB items with the specified SongTitle and Artist.

$invokeDDBQuery = @{
    TableName = 'Music'
    KeyConditionExpression = ' SongTitle = :SongTitle and Artist = :Artist'
    ExpressionAttributeValues = @{
        ':SongTitle' = 'Somewhere Down The Road'
        ':Artist' = 'No One You Know'
    } | ConvertTo-DDBItem
}
Invoke-DDBQuery @invokeDDBQuery | ConvertFrom-DDBItem

Output:

Name                           Value
----                           -----
Genre                          Country
Artist                         No One You Know
Price                          1.94
CriticRating                   9
SongTitle                      Somewhere Down The Road
AlbumTitle                     Somewhat Famous

Query items by using a key condition expression.

class Movies:
    """Encapsulates an Amazon DynamoDB table of movie data.

    Example data structure for a movie record in this table:
        {
            "year": 1999,
            "title": "For Love of the Game",
            "info": {
                "directors": ["Sam Raimi"],
                "release_date": "1999-09-15T00:00:00Z",
                "rating": 6.3,
                "plot": "A washed up pitcher flashes through his career.",
                "rank": 4987,
                "running_time_secs": 8220,
                "actors": [
                    "Kevin Costner",
                    "Kelly Preston",
                    "John C. Reilly"
                ]
            }
        }
    """

    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"]

Query items and project them to return a subset of data.

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"]

class DynamoDBBasics
  attr_reader :dynamo_resource, :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

Find the movies made in the specified year.

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![])
    }
}

    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.

import AWSDynamoDB


    /// 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] {
        do {
            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
            )
            // Use "Paginated" to get all the movies.
            // This lets the SDK handle the 'lastEvaluatedKey' property in "QueryOutput".

            let pages = client.queryPaginated(input: input)

            var movieList: [Movie] = []
            for try await page in pages {
                guard let items = page.items else {
                    print("Error: no items returned.")
                    continue
                }

                // Convert the found movies into `Movie` objects and return an array
                // of them.

                for item in items {
                    let movie = try Movie(withItem: item)
                    movieList.append(movie)
                }
            }
            return movieList
        } catch {
            print("ERROR: getMovies:", dump(error))
            throw error
        }
    }