Execute a query with the Azure Cosmos DB for NoSQL SDK

The latest version of the JavaScript SDK for Azure Cosmos DB for NoSQL simplifies querying a container and iterating over result sets using JavaScript’s modern features.

The @azure/cosmos library has built-in functionality to make querying Azure Cosmos DB efficient and straightforward.

In this lab, you’ll use an iterator to process a large result set returned from Azure Cosmos DB for NoSQL. You will use the JavaScript SDK to query and iterate over results.

Prepare your development environment

If you have not already cloned the lab code repository for Build copilots with Azure Cosmos DB and set up your local environment, view the Setup local lab environment instructions to do so.

Create an Azure Cosmos DB for NoSQL account

If you already created an Azure Cosmos DB for NoSQL account for the Build copilots with Azure Cosmos DB labs on this site, you can use it for this lab and skip ahead to the next section. Otherwise, view the Setup Azure Cosmos DB instructions to create an Azure Cosmos DB for NoSQL account that you will use throughout the lab modules and grant your user identity access to manage data in the account by assigning it to the Cosmos DB Built-in Data Contributor role.

Create Azure Cosmos DB database and container with sample data

If you already created an Azure Cosmos DB database named cosmicworks-full and container within it named products, which is preloaded with sample data, you can use it for this lab and skip ahead to the next section. Otherwise, follow the steps below to create a new sample database and container.

Import the @azure/cosmos library

The @azure/cosmos library is available on npm for easy installation into your JavaScript projects.

1. In Visual Studio Code, in the Explorer pane, browse to the javascript/05-sdk-queries folder.

2. Open the context menu for the javascript/05-sdk-queries folder and then select Open in Integrated Terminal to open a new terminal instance.

   📝 This command will open the terminal with the starting directory already set to the javascript/05-sdk-queries folder.

3. Initialize a new Node.js project:

    npm init -y
   

4. Install the @azure/cosmos package using the following command:

    npm install @azure/cosmos
   

5. Install the @azure/identity library, which allows us to use Azure authentication to connect to the Azure Cosmos DB workspace, using the following command:

    npm install @azure/identity
   

Iterate over the results of a SQL query using the SDK

Using the credentials from the newly created account, you will connect with the SDK classes and connect to the database and container you provisioned in an earlier step, and iterate over the results of a SQL query using the SDK.

You will now use an iterator to create a simple-to-understand loop over paginated results from Azure Cosmos DB. Behind the scenes, the SDK will manage the feed iterator and ensure subsequent requests are invoked correctly.

1. In Visual Studio Code, in the Explorer pane, browse to the javascript/05-sdk-queries folder.

2. Open the empty JavaScript file named script.js.

3. Add the following require statements to import the @azure/cosmos and @azure/identity libraries:

    const { CosmosClient } = require("@azure/cosmos");
    const { DefaultAzureCredential  } = require("@azure/identity");
    process.env.NODE_TLS_REJECT_UNAUTHORIZED = 0
   

4. Add variables named endpoint and credential and set the endpoint value to the endpoint of the Azure Cosmos DB account you created earlier. The credential variable should be set to a new instance of the DefaultAzureCredential class:

    const endpoint = "<cosmos-endpoint>";
    const credential = new DefaultAzureCredential();
   

   📝 For example, if your endpoint is: https://dp420.documents.azure.com:443/, the statement would be: const endpoint = “https://dp420.documents.azure.com:443/”;.

5. Add a new variable named client and initialize it as a new instance of the CosmosClient class using the endpoint and credential variables:

    const client = new CosmosClient({ endpoint, aadCredentials: credential });
   

6. Create a new method named queryContainer and code to execute that method when you run the script. You will add the code to query the container within this method:

    async function queryContainer() {
        // Query the container
    }
   
    queryContainer().catch((error) => {
        console.error(error);
    });
   

7. Inside the queryContainer method, add the following code to connect to the database and container you created earlier::

    const database = client.database("cosmicworks-full");
    const container = database.container("products");
   

8. Create a query string variable named sql with a value of SELECT * FROM products p.

    const sql = "SELECT * FROM products p";
   

9. Invoke the query method with the sql variable as a parameter to the constructor. The enableCrossPartitionQuery parameter, when set to true, allows sending more than one request to execute the query in the Azure Cosmos DB service. More than one request is necessary if the query is not scoped to a single partition key value.

    const iterator = container.items.query(
        query,
        { enableCrossPartitionQuery: true }
    );
   

10. Iterate over the paginated results and print the id, name, and price of each item:

     while (iterator.hasMoreResults()) {
         const { resources } = await iterator.fetchNext();
         for (const item of resources) {
             console.log(`[${item.id}]	${item.name.padEnd(35)}	${item.price.toFixed(2)}`);
         }
     }
    

11. Your script.js file should now look like this:

     const { CosmosClient } = require("@azure/cosmos");
     const { DefaultAzureCredential  } = require("@azure/identity");
     process.env.NODE_TLS_REJECT_UNAUTHORIZED = 0
    
     const endpoint = "<cosmos-endpoint>";
     const credential = new DefaultAzureCredential();
    
     const client = new CosmosClient({ endpoint, aadCredentials: credential });
    
     async function queryContainer() {
         const database = client.database("cosmicworks-full");
         const container = database.container("products");
            
         const query = "SELECT * FROM products p";
        
         const iterator = container.items.query(
             query,
             { enableCrossPartitionQuery: true }
         );
            
         while (iterator.hasMoreResults()) {
             const { resources } = await iterator.fetchNext();
             for (const item of resources) {
                 console.log(`[${item.id}]	${item.name.padEnd(35)}	${item.price.toFixed(2)}`);
             }
         }
     }
        
     queryContainer().catch((error) => {
         console.error(error);
     });
    

12. Save the script.js file.

13. Before running the script, you must log into Azure using the az login command. At the terminal window, run:

     az login
    

14. Run the script to create the database and container:

     node script.js
    

15. The script will now output every product in the container.

16. Close the integrated terminal.

17. Close Visual Studio Code.