Query a feature layer (SQL)

Learn how to execute a SQL query to access polygon features from a feature layer.

A feature layer can contain a large number of features stored in ArcGIS. To access a subset of the features, you can execute a SQL or spatial query, or both at the same time. You can also return the attributes, geometry, or both attributes and geometry for each record. SQL and spatial queries are useful when a feature layer is very large and you just want to access a subset of the data.

In this tutorial, you perform server-side SQL queries to return a subset of the features from the LA County Parcel hosted feature layer. The feature layer contains over 2.4 million features. The resulting features are displayed as graphics 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

Create a new pen

To get started, you can complete the Display a map tutorial or use the .

Get an access token

You need an access token with the correct privileges to access the resources used in this tutorial.

Go to the Create an API key tutorial and create an API key with the following privilege(s):
- 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 credentials access to the layer item. Learn more in Item access privileges.
Copy the API key access token to your clipboard when prompted.

In CodePen, update the accessToken variable to use your access token.

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const accessToken = "YOUR_ACCESS_TOKEN";
const basemapEnum = "arcgis/outdoor";
const map = new maplibregl.Map({
  container: "map", // the id of the div element
  style: `https://basemapstyles-api.arcgis.com/arcgis/rest/services/styles/v2/styles/${basemapEnum}?token=${accessToken}`,
  zoom: 12, // starting zoom
  center: [-118.805, 34.027] // starting location [longitude, latitude]
});

Run the code to ensure the basemap is displayed in the map.

To learn about the other types of authentication available, go to Types of authentication.

Add API 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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    <script src=https://unpkg.com/maplibre-gl@4/dist/maplibre-gl.js></script>
    <link href=https://unpkg.com/maplibre-gl@4/dist/maplibre-gl.css rel="stylesheet" />

    <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
        style: `https://basemapstyles-api.arcgis.com/arcgis/rest/services/styles/v2/styles/${basemapEnum}?token=${accessToken}`,
        zoom: 12, // starting zoom

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

      });

      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 GeoJSON polygons. You can display them with a GeoJSON source and a fill layer.

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 attribution for the feature layer source.

Go to the LA County Parcels item.
Scroll down to the Credits (Attribution) section and copy its value.

Create an attribution property and paste the attribution value from the item.

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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-devlabs.maps.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 layer that match the selected where clause.

To limit the query results to the visible extent of the Map, you can set the queryFeatures geometry property. To do so, use map.getBounds to get the extent of the Map viewport, and then convert it to the required esriGeometryEnvelope format of [minx, miny, maxx, maxy]. This confines the SQL query to the geographic bounds (extent) of the map.

When the matching parcels are returned, call setData on the parcels source to display them.

Create a function called executeQuery with whereClause and geometry parameters. Inside, create a new arcgisRest.ApiKeyManager to access the feature service. Call arcgisRest.queryFeatures. Pass the geometry and geometryType. Specify GeoJSON as the return type, requesting returnGeometry and specific outFields. All of the features within the geometry will be returned with attribute information set by the outFields property.

There are many other spatial relationships that you can specify with spatialRel. For example, you can use esriSpatialRelContains to only return parcels completely within the viewport. See the ArcGIS services reference for details.

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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 layer 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.

See the Display a pop-up tutorial for more details.

Add a click event handler to the parcels-fill layer. Inside, construct the pop-up content from the attributes of the clicked parcel. Create a new Popup, then use popup.setHTML to set the content. 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

In CodePen, run your code to display the map.

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's attributes.

What's next?

Learn how to use additional ArcGIS location services in these tutorials:

Query a feature layer (spatial)

Execute a spatial query to access polygon features from a feature service.

Get global data

Query demographic information for locations around the world with the GeoEnrichment service.

Get local data

Query regional facts, spending trends, and psychographics with the GeoEnrichment service.

Add a feature layer

Add features from feature layers to a map.

Style a feature layer

Use data-driven styling to apply symbol colors and styles to feature layers.