---
title: Querying from a Worker
description: Access Analytics Engine data from within a Worker.
image: https://developers.cloudflare.com/core-services-preview.png
---

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# Querying from a Worker

If you want to access Analytics Engine data from within a Worker you can use `fetch` to access the SQL API. The API can return JSON data that is easy to interact with in JavaScript.

## Authentication

In order that your Worker can authenticate with the API you will need your account ID and an API token.

* Your 32 character account ID can be obtained from the Cloudflare dashboard.
* An API token can also be generated in the dashboard. Refer to the [SQL API docs](https://developers.cloudflare.com/analytics/analytics-engine/sql-api/#authentication) for more information on this.

We recommend storing the account ID as an environment variable and the API token as a secret in your worker. This can be done through the dashboard or through Wrangler. Refer to the [Workers documentation](https://developers.cloudflare.com/workers/configuration/environment-variables/) for more details on this.

## Querying

Use the JavaScript `fetch` API as follows to execute a query:

JavaScript

```

const query = "SELECT * FROM my_dataset";

const API = `https://api.cloudflare.com/client/v4/accounts/${env.ACCOUNT_ID}/analytics_engine/sql`;

const response = await fetch(API, {

  method: "POST",

  headers: {

    Authorization: `Bearer ${env.API_TOKEN}`,

  },

  body: query,

});

const responseJSON = await response.json();


```

The data will be returned in the format described in the [FORMAT](https://developers.cloudflare.com/analytics/analytics-engine/sql-reference/statements/#json) section of the documentation, allowing you to extract meta information about the names and types of returned columns in addition to the data itself and a row count.

## Example Worker

The following is a sample Worker which executes a query against a dataset of weather readings and displays minimum and maximum values for each city.

### Environment variable setup

First the environment variables are set up with the account ID and API token.

The account ID is set in the [Wrangler configuration file](https://developers.cloudflare.com/workers/wrangler/configuration/):

* [  wrangler.jsonc ](#tab-panel-4484)
* [  wrangler.toml ](#tab-panel-4485)

JSONC

```

{

  "vars": {

    "ACCOUNT_ID": "<account_id>"

  }

}


```

TOML

```

[vars]

ACCOUNT_ID = "<account_id>"


```

The API\_TOKEN can be set as a secret, using the wrangler command line tool, by running the following and entering your token string:

Terminal window

```

npx wrangler secret put API_TOKEN


```

### Worker script

The worker script itself executes a query and formats the result:

JavaScript

```

export default {

  async fetch(request, env) {

    // This worker only responds to requests at the root.

    if (new URL(request.url).pathname != "/") {

      return new Response("Not found", { status: 404 });

    }


    // SQL string to be executed.

    const query = `

            SELECT

                blob1 AS city,

                max(double1) as max_temp,

                min(double1) as min_temp

            FROM weather

            WHERE timestamp > NOW() - INTERVAL '1' DAY

            GROUP BY city

            ORDER BY city`;


    // Build the API endpoint URL and make a POST request with the query string

    const API = `https://api.cloudflare.com/client/v4/accounts/${env.ACCOUNT_ID}/analytics_engine/sql`;

    const queryResponse = await fetch(API, {

      method: "POST",

      headers: {

        Authorization: `Bearer ${env.API_TOKEN}`,

      },

      body: query,

    });


    // The API will return a 200 status code if the query succeeded.

    // In case of failure we log the error message and return a failure message.

    if (queryResponse.status != 200) {

      console.error("Error querying:", await queryResponse.text());

      return new Response("An error occurred!", { status: 500 });

    }


    // Read the JSON data from the query response and render the data as HTML.

    const queryJSON = await queryResponse.json();

    return new Response(renderResponse(queryJSON.data), {

      headers: { "content-type": "text/html" },

    });

  },

};


// renderCity renders a table row as HTML from a data row.

function renderCity(row) {

  return `<tr><td>${row.city}</td><td>${row.min_temp}</td><td>${row.max_temp}</td></tr>`;

}


// renderResponse renders a simple HTML table of results.

function renderResponse(data) {

  return `<!DOCTYPE html>

<html>

    <body>

        <table>

            <tr><th>City</th><th>Min Temp</th><th>Max Temp</th></tr>

            ${data.map(renderCity).join("\n")}

        </table>

    </body>

<html>`;

}


```

```json
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/analytics/","name":"Analytics"}},{"@type":"ListItem","position":3,"item":{"@id":"/analytics/analytics-engine/","name":"Workers Analytics Engine"}},{"@type":"ListItem","position":4,"item":{"@id":"/analytics/analytics-engine/worker-querying/","name":"Querying from a Worker"}}]}
```