Query a feature layer (SQL) | MapLibre GL JS

Learn how to query a feature layer with SQL.

Query a feature layer with SQL using API key authentication

A feature layerA feature layer (client-side) is a data layer that can access and display features from a feature service that has the same type of geometry and attribute fields.Learn more can contain a large number of featuresA feature is a single record, also known as a row, that represents a real-world entity. It typically contains a geometry (point, multipoint, polyline, or polygon) and attributes but it can also contain just attributes.Learn more stored in ArcGISArcGIS is the brand name for all of the desktop, server, and developer products and technologies offered by Esri.Learn more. To access a subset of the features, you can execute a SQL or spatial query, or both at the same time.

In this tutorial, you perform server-side SQL queries to return a subset of the featuresA feature is a single record, also known as a row, that represents a real-world entity. It typically contains a geometry (point, multipoint, polyline, or polygon) and attributes but it can also contain just attributes.Learn more from the LA County Parcel hosted feature layerA hosted feature layer is a hosted layer (item) in a portal that is used to manage the properties and settings of a spatially-enabled feature layer in a feature service.Learn more. The resulting featuresA feature is a single record, also known as a row, that represents a real-world entity. It typically contains a geometry (point, multipoint, polyline, or polygon) and attributes but it can also contain just attributes.Learn more are displayed as graphicsA graphic is a visual element composed of a geometry, symbol, and attributes that is displayed on a map or scene.Learn more on the map. A pop-up is also used to display feature attributes.

Prerequisites

You need an ArcGIS Location Platform or ArcGIS Online account.

Steps

Get the starter app

Select a type of authentication and follow the steps to create a new app.

Choose API key authentication if you:

Want the easiest way to get started.
Want to build public applicationsA public application is an application that allows anonymous access without requiring users to sign in with an ArcGIS account. It supports API key or app authentication.Learn more that access ArcGIS Location ServicesArcGIS Location Services, also referred to as Location Services, are services hosted by Esri that provide geospatial functionality for developing mapping applications. They include the ArcGIS Basemap Styles service, ArcGIS Static Basemap Tiles service, ArcGIS Places service, ArcGIS Geocoding service, ArcGIS Routing service, ArcGIS GeoEnrichment service, and ArcGIS Elevation service. An ArcGIS Location Platform or ArcGIS Online account is required to use the services.Learn more and secure itemsAn item, also known as a content item, is a resource stored in a portal such as a web map, hosted layer, style, script tool, file, or notebook.Learn more.
Have an ArcGIS Location Platform or ArcGIS Online account.

Choose user authentication if you:

Want to build private applications.
Require application users to sign in with their own ArcGIS accountAn ArcGIS account is an identity with a user type and set of privileges that can access specific ArcGIS products, tools, APIs, services, and resources. The main account types that can be used for development are an ArcGIS Location Platform account, ArcGIS Online account, and ArcGIS Enterprise account. ArcGIS Location Platform and ArcGIS Online accounts are also associated with a subscription.Learn more and access resources their behalf.
Have an ArcGIS Online account.

To learn more about both types of authentication, go to Authentication.

You can choose one of the following to create a new CodePen:

Option 1: Complete the Display a map tutorial; or,
Option 2: Start from the Display a map tutorial .

Set up authentication

Create a new API key credentialAPI key credentials are an item that contains the parameters used to create and manage long-lived access tokens for API key authentication. They are a type of developer credential.Learn more with the correct privileges to get an access token.

Go to the Create an API key tutorial to follow the steps to get an access token with these privilege(s)Privileges are a set of permissions assigned to ArcGIS accounts, developer credentials, and applications that grant access to secure resources and functionality in ArcGIS.Learn more:
- Privileges
  - Location services > Basemaps
- Item access
  - Note: If you are using your own custom data layer for this tutorial, you need to grant the API key credentialsAPI key credentials are an item that contains the parameters used to create and manage long-lived access tokens for API key authentication. They are a type of developer credential.Learn more access to the layer item. Learn more in Item access privileges.

Create a new OAuth credentialOAuth credentials are an item that contains parameters required to implement user authentication or app authentication, including a client_id, client_secret, and redirect URIs. They are a type of developer credential.Learn more to register the application.

Go to the Create OAuth credentials for user authentication tutorial to create an OAuth credential.
Copy the Client ID and Redirect URL from your OAuth credentials item and paste them to a safe location. They will be used in a later step.

Set developer credentials

Use the API key or OAuth developer credentialsDeveloper credentials are a type of item in a portal that contains parameters for authentication. There are two types of developer credentials: API key credentials and OAuth credentials.Learn more so your application can access ArcGIS servicesA service, also known as an ArcGIS service, is software that supports an ArcGIS REST API and provides geospatial functionality or data. A service can be hosted by Esri or in ArcGIS Enterprise.Learn more.

Update the accessToken variable to use your API key.

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    /* Use for API key authentication */
    const accessToken = "YOUR_ACCESS_TOKEN";
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In both the index.html and callback.html files, replace YOUR_CLIENT_ID and YOUR_REDIRECT_URL with the client ID and redirect URL of your OAuth credentialsOAuth credentials are an item that contains parameters required to implement user authentication or app authentication, including a client_id, client_secret, and redirect URIs. They are a type of developer credential.Learn more.

index.html
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    /* Use for user authentication */
    const clientId = "YOUR_CLIENT_ID"; // Your client ID from OAuth credentials
    const redirectUri = ""YOUR_REDIRECT_URI""; // The redirect URL registered in your OAuth credentials
    const session = await arcgisRest.ArcGISIdentityManager.beginOAuth2({
      clientId,
      redirectUri,
      portal: "https://www.arcgis.com/sharing/rest" // Your portal URL
    });

    const accessToken = session.token;

callback.html
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    arcgisRest.ArcGISIdentityManager.completeOAuth2({
      clientId: "YOUR_CLIENT_ID", // Your client ID from OAuth credentials
      redirectUri: "YOUR_REDIRECT_URI", // The redirect URL registered in your OAuth credentials
      portal: "https://www.arcgis.com/sharing/rest" // Your portal URL
    });

Run the app and ensure you can sign in successfully.

If you are unable to sign in, make sure you have the correct redirect URL and port. This URL varies based on your application and typically takes the format of https://<server>[:port]/callback.html or http://my-arcgis-app:/auth. For example, if you are running an application on http://127.0.0.1:5500/, set http://127.0.0.1:5500/callback.html as your redirect URL in the index.html and callback.html file and your developer credential. They all have to match!

Add script references

This tutorial uses ArcGIS REST JS to query the feature layer.

In the <head> element, add references to the ArcGIS REST JS library.

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    <!-- Load MapLibre GL JS from CDN -->
    <script src="https://unpkg.com/maplibre-gl@5.23.0/dist/maplibre-gl.js"></script>
    <link href="https://unpkg.com/maplibre-gl@5.23.0/dist/maplibre-gl.css" rel="stylesheet">
    <!-- Load MapLibre ArcGIS from CDN -->
    <script src="https://unpkg.com/@esri/maplibre-arcgis@1.1.0/dist/umd/maplibre-arcgis.min.js"></script>

    <script src="https://unpkg.com/@esri/arcgis-rest-request@4/dist/bundled/request.umd.js"></script>
    <script
      src="https://unpkg.com/@esri/arcgis-rest-feature-service@4/dist/bundled/feature-service.umd.js"></script>

    <style>
    html,
    body,
    #map {
      padding: 0;
      margin: 0;
      height: 100%;
      width: 100%;
      font-family: Arial, Helvetica, sans-serif;
      font-size: 14px;
      color: #323232;
    }

    </style>
  </head>
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Create a SQL selector

Hosted feature layers support a standard SQL query where clause. Use an HTML <select> element to provide a list of SQL queries for the LA County Parcel feature layer.

To add the <select> HTML element as a Map control, you create an object that implements the MapLibre GL JS IControl interface.

Creating an IControl allows MapLibre GL JS to position it, which prevents your control overlapping other MapLibre GL JS controls.

Create a QueryControl class with an onAdd function. Inside, create a <div> element with a <select> inside, with options for each of the SQL where clauses. Return this element.

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    const map = new maplibregl.Map({
      container: "map", // the id of the div element
      zoom: 12, // starting zoom

      center: [-118.80543, 34.03] // starting location [longitude, latitude]

    });
    const basemapStyle = maplibreArcGIS.BasemapStyle.applyStyle(map, {
      style: "arcgis/outdoor",
      token: accessToken
    });

    class QueryControl {
      onAdd(map) {
        const template = document.createElement("template");
        template.innerHTML = `<div class="maplibregl-ctrl maplibregl-ctrl-group" style="margin:20px;">
            <select style="font-size:16px; padding:4px 8px;">
              <option value="">Choose a WHERE clause...</option>
              <option>UseType = 'Residential'</option>
              <option>UseType = 'Government'</option>
              <option>UseType = 'Irrigated Farm'</option>
              <option>TaxRateArea = 10853</option>
              <option>TaxRateArea = 10860</option>
              <option>TaxRateArea = 08637</option>
              <option>Roll_LandValue > 1000000</option>
              <option>Roll_LandValue < 1000000</option>
            </select>
          </div>`;

        return template.content;
      }
    }
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Create a QueryControl and add it to the Map with map.addControl.

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        return template.content;
      }
    }

    const queryControl = new QueryControl();
    map.addControl(queryControl);
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Add parcel layer

Parcels returned by the query are simple GeoJSONGeoJSON is an open standard for representing geographic information in a JSON file. It is commonly used for sharing data between web services or manipulating vector data in the browser.Learn more polygons. You can display them with a GeoJSONGeoJSON is an open standard for representing geographic information in a JSON file. It is commonly used for sharing data between web services or manipulating vector data in the browser.Learn more sourceA source in Mapbox GL JS is a file or service that supplies data for a layer displayed in a map.Learn more and a fill layerA layer in Mapbox GL JS is a visual element that displays data from a source.Learn more.

Create an addParcelLayer function. Inside, add a GeoJSON source and a fill layer. Add the layer before the first symbol layer.

By inserting the polygon layer beneath the icon and text layers, it keeps the labels readable. In MapLibre GL JS, there is no distinction between "basemap" layers and "overlay layers", so you can insert the layer anywhere.

To determine the first symbol layer, you can use map.getStyle to get the style, then iterate to find the first layer whose type is symbol.

See the MapLibre GL JS documentation for details.

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    const queryControl = new QueryControl();
    map.addControl(queryControl);

    function addParcelLayer() {
      map.addSource("parcels", {
        type: "geojson",
        data: {
          type: "FeatureCollection",
          features: []
        },

      });

      const firstSymbolLayer = map.getStyle().layers.find((l) => l.type === "symbol");
      map.addLayer(
        {
          id: "parcels-fill",
          source: "parcels",
          type: "fill",
          paint: {
            "fill-color": "hsla(200, 80%,50%, 0.5)",

            "fill-outline-color": "hsl(360, 100%, 100%)"
          }
        },
        firstSymbolLayer.id
      ); // insert new layer before this one
      map.addLayer({
        id: "parcels-line",
        source: "parcels",
        type: "line",
        paint: {
          "line-width": 0.5,
          "line-color": "hsl(360, 100%,100%)"
        }
      }); // set outline style for parcels
    }
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Add the data attributionData attribution is the requirement to display the names of data source providers in all applications when accessing ArcGIS content, layers, or services.Learn more for the feature layer source.

Go to the LA County Parcels itemAn item, also known as a content item, is a resource stored in a portal such as a web map, hosted layer, style, script tool, file, or notebook.Learn more.
Scroll down to the Acknowledgments section and copy its value.

Paste the copied value to the attribution property.

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    const queryControl = new QueryControl();
    map.addControl(queryControl);

    function addParcelLayer() {
      map.addSource("parcels", {
        type: "geojson",
        data: {
          type: "FeatureCollection",
          features: []
        },

        // Attribution text retrieved from https://arcgis.com/home/item.html?id=a6fdf2ee0e454393a53ba32b9838b303
        attribution: "LA County Parcels"

      });

      const firstSymbolLayer = map.getStyle().layers.find((l) => l.type === "symbol");
      map.addLayer(
        {
          id: "parcels-fill",
          source: "parcels",
          type: "fill",
          paint: {
            "fill-color": "hsla(200, 80%,50%, 0.5)",

            "fill-outline-color": "hsl(360, 100%, 100%)"
          }
        },
        firstSymbolLayer.id
      ); // insert new layer before this one
      map.addLayer({
        id: "parcels-line",
        source: "parcels",
        type: "line",
        paint: {
          "line-width": 0.5,
          "line-color": "hsl(360, 100%,100%)"
        }
      }); // set outline style for parcels
    }
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Add load handler

To add layers to the map, you need to use the load event to ensure the map is fully loaded.

Add an event handler for the load event. Inside, call addParcelLayer.

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      const firstSymbolLayer = map.getStyle().layers.find((l) => l.type === "symbol");
      map.addLayer(
        {
          id: "parcels-fill",
          source: "parcels",
          type: "fill",
          paint: {
            "fill-color": "hsla(200, 80%,50%, 0.5)",

            "fill-outline-color": "hsl(360, 100%, 100%)"
          }
        },
        firstSymbolLayer.id
      ); // insert new layer before this one
      map.addLayer({
        id: "parcels-line",
        source: "parcels",
        type: "line",
        paint: {
          "line-width": 0.5,
          "line-color": "hsl(360, 100%,100%)"
        }
      }); // set outline style for parcels
    }

    map.on("load", () => {

      addParcelLayer();

    });
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Execute the query

Use the ArcGIS REST JS queryFeatures method to find features in the LA County Parcels feature layerA feature layer (client-side) is a data layer that can access and display features from a feature service that has the same type of geometry and attribute fields.Learn more that match the selected where clause.

To limit the query results to the visible extentAn extent is a bounding rectangle with points that delineate an area for a map or scene.Learn more of the Map, you can set geometry property. This confines the SQL query to the geographic bounds (extent) of the map.

When the matching parcels are returned, call setData on the parcels sourceA source in Mapbox GL JS is a file or service that supplies data for a layer displayed in a map.Learn more to display them.

Create a function that calls arcgisRest.queryFeatures. Specify GeoJSONGeoJSON is an open standard for representing geographic information in a JSON file. It is commonly used for sharing data between web services or manipulating vector data in the browser.Learn more as the return type, requesting returnGeometry and specific outFields. All of the featuresA feature is a single record, also known as a row, that represents a real-world entity. It typically contains a geometry (point, multipoint, polyline, or polygon) and attributes but it can also contain just attributes.Learn more within the geometryA geometry is a geometric shape, such as a point, polyline, or polygon, that contains one or more coordinates and a spatial reference.Learn more will be returned with attributeAttributes are fields and values for a single feature or non-spatial record. They are typically stored in a database or service such as a feature service.Learn more information set by the outFields property.

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    function executeQuery(whereClause, geometry) {

      arcgisRest
        .queryFeatures({
          url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/LA_County_Parcels/FeatureServer/0",
          geometry: geometry,
          geometryType: "esriGeometryEnvelope",
          inSR: 4326, // EPSG:4326 uses latitudes and longitudes
          spatialRel: "esriSpatialRelIntersects",
          where: whereClause,
          f: "geojson",
          returnGeometry: true,
          outFields: ["APN", "UseType", "TaxRateCity", " Roll_LandValue"]
        })

    }
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Add a response handler. Inside, set the returned parcels as the data for the parcels source.

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      arcgisRest
        .queryFeatures({
          url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/LA_County_Parcels/FeatureServer/0",
          geometry: geometry,
          geometryType: "esriGeometryEnvelope",
          inSR: 4326, // EPSG:4326 uses latitudes and longitudes
          spatialRel: "esriSpatialRelIntersects",
          where: whereClause,
          f: "geojson",
          returnGeometry: true,
          outFields: ["APN", "UseType", "TaxRateCity", " Roll_LandValue"]
        })

        .then((response) => {
          map.getSource("parcels").setData(response);
        });
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Update your QueryControl to add a change event handler to the select element. Inside, calculate the viewport extent and call executeQuery with the extent and where clause.

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    class QueryControl {
      onAdd(map) {
        const template = document.createElement("template");
        template.innerHTML = `<div class="maplibregl-ctrl maplibregl-ctrl-group" style="margin:20px;">
            <select style="font-size:16px; padding:4px 8px;">
              <option value="">Choose a WHERE clause...</option>
              <option>UseType = 'Residential'</option>
              <option>UseType = 'Government'</option>
              <option>UseType = 'Irrigated Farm'</option>
              <option>TaxRateArea = 10853</option>
              <option>TaxRateArea = 10860</option>
              <option>TaxRateArea = 08637</option>
              <option>Roll_LandValue > 1000000</option>
              <option>Roll_LandValue < 1000000</option>
            </select>
          </div>`;

        const select = template.content.querySelector("select");
        select.addEventListener("change", () => {
          // Do nothing for the "Choose a WHERE clause..." option
          if (select.value !== "") {
            // Get bounds in [minx, miny, maxx, maxy] format
            const bounds = map.getBounds().toArray().flat();
            executeQuery(select.value, bounds);
          }
        });

        return template.content;
      }
    }
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At the top right, click Run. When you select a where clause using the toolbox, a query will run against the feature layerA feature layer (client-side) is a data layer that can access and display features from a feature service that has the same type of geometry and attribute fields.Learn more and display all land parcels within the current viewport matching the where clause.

Add a pop-up

You can add a Popup to view attributes of a parcel when the user clicks on it.

Add a click event handler to the parcels-fill layer. Inside, create a popup that display the attributes of the clicked parcel. Set the position of the pop-up and add it to the map.

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        .then((response) => {
          map.getSource("parcels").setData(response);
        });

    }

    map.on("click", "parcels-fill", (e) => {
      const parcel = e.features[0].properties;
      const landValue = parcel.Roll_LandValue != "null" ? `$${parcel.Roll_LandValue.toLocaleString()}` : "N/A";
      const message =
        `<b>Parcel ${parcel.APN}</b></br>` +
        `Type: ${parcel.UseType} <br>` +
        `Land value: ${landValue} <br>` +
        `Tax Rate City: ${parcel.TaxRateCity}`;

      new maplibregl.Popup().setHTML(message).setLngLat(e.lngLat).addTo(map);
    });
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Run the app

Run the app.

When the map displays, you should be able to use the query selector to display parcels. Click on a parcel to show a pop-up with the feature attributes.