DP-420 Designing and Implementing Native Applications Using Microsoft Azure Cosmos DB

Implement queries based on variable data

Concepts

Azure Cosmos DB is a powerful and flexible NoSQL database service provided by Microsoft Azure. It offers a variety of APIs and supports querying based on variable data. In this article, we will explore how to design and implement native applications using Azure Cosmos DB, focusing specifically on implementing queries based on variable data.

Getting Started

To get started, you need to have a basic understanding of Azure Cosmos DB and its fundamentals. If you are new to Azure Cosmos DB, I recommend referring to the official Microsoft documentation for a comprehensive introduction.

Once you have set up your Azure Cosmos DB account and created a database with a container, you can start implementing queries based on variable data.

Create Documents

To execute queries, you need to have documents in your container. Documents in Azure Cosmos DB are JSON objects. You can create documents using various programming languages and frameworks, such as .NET, Java, Python, or Node.js. Here’s an example of creating a document using the .NET SDK:

using Microsoft.Azure.Cosmos; using System; using System.Threading.Tasks;


static async Task Main(string[] args)

{

    string endpointUrl = "your-endpoint-url";

    string authorizationKey = "your-authorization-key";

    string databaseName = "your-database-name";

    string containerName = "your-container-name";

    using (CosmosClient client = new CosmosClient(endpointUrl, authorizationKey))

    {

        Database database = await client.CreateDatabaseIfNotExistsAsync(databaseName);

        Container container = await database.CreateContainerIfNotExistsAsync(containerName, "/id");
        dynamic document = new

        {

            id = Guid.NewGuid().ToString(),

            name = "John Doe",

            age = 30,

            city = "Seattle"

        };
        ItemResponse response = await container.CreateItemAsync(document);

Console.WriteLine($"Created document with id: {response.Resource.id}"); } }

Query Documents

Once you have inserted documents into your container, you can query them using SQL-based queries. Azure Cosmos DB supports a rich set of query capabilities, including filtering, sorting, aggregations, and more. Here’s an example of querying documents based on variable data using the SQL API:

using Microsoft.Azure.Cosmos; using System; using System.Collections.Generic; using System.Linq; using System.Threading.Tasks;


static async Task Main(string[] args)

{

    string endpointUrl = "your-endpoint-url";

    string authorizationKey = "your-authorization-key";

    string databaseName = "your-database-name";

    string containerName = "your-container-name";
    using (CosmosClient client = new CosmosClient(endpointUrl, authorizationKey))

    {

        Database database = await client.CreateDatabaseIfNotExistsAsync(databaseName);

        Container container = await database.CreateContainerIfNotExistsAsync(containerName, "/id");
        string cityName = "Seattle";

        QueryDefinition queryDefinition = new QueryDefinition("SELECT * FROM c WHERE c.city = @cityName")

            .WithParameter("@cityName", cityName);
        List results = new List();
        using (FeedIterator resultSetIterator = container.GetItemQueryIterator(queryDefinition))

        {

            while (resultSetIterator.HasMoreResults)

            {

                FeedResponse response = await resultSetIterator.ReadNextAsync();

                results.AddRange(response.Resource);

            }

        }

        Console.WriteLine($"Found {results.Count} documents matching the query.");

foreach (dynamic document in results) { Console.WriteLine($"Document - id: {document.id}, name: {document.name}, age: {document.age}"); } } }

In this example, we create a SQL query that retrieves documents where the city attribute matches the provided city name variable. The query parameter is specified using the @cityName syntax. The results are iterated using a FeedIterator and printed to the console.

By using variables in your queries, you can dynamically retrieve data based on user input or other dynamic criteria.

These examples demonstrate the basic implementation of querying based on variable data in native applications using Azure Cosmos DB. However, Azure Cosmos DB offers much more advanced query capabilities, including user-defined functions, stored procedures, and indexing policies.

I encourage you to explore the Microsoft documentation further to learn more about designing and implementing native applications using Azure Cosmos DB and its query capabilities. Happy coding!