Query features with SQL | OpenLayers

Learn how to execute a SQL query to a feature layer.

Make a SQL query to a feature layer using API key authentication

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

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 applications that access ArcGIS Location Services and secure items.
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 account 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 credential with the correct privileges to get an access token.

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.

Set developer credentials

Use the API key or OAuth developer credentials so your application can access ArcGIS services.

Update the accessToken variable to use your API key.

Expand
Use dark colors for code blocks
    /* Use for API key authentication */
    const accessToken = "YOUR_ACCESS_TOKEN";
Expand

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 credentials.

index.html
Use dark colors for code blocks
    /* 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
Use dark colors for code blocks
    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 references

This tutorial uses ArcGIS REST JS to query the feature layer, and the ol-popup library to display pop-ups.

In the <head> element, add references to the ArcGIS REST JS and ol-popup libraries.

Expand
Use dark colors for code blocks
    <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/ol@v10.7.0/ol.css">
    <script src="https://cdn.jsdelivr.net/npm/ol@v10.7.0/dist/ol.js"></script>
    <script src="https://cdn.jsdelivr.net/npm/ol-mapbox-style@13.1.1/dist/olms.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>
    <script src="https://unpkg.com/ol-popup@5.1.1/dist/ol-popup.js"></script>
    <link rel="stylesheet" href="https://unpkg.com/ol-popup@5.1.1/src/ol-popup.css">
Expand

Create a SQL selector

ArcGIS 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.

Create a select element containing an option element for each where clause.

Expand
Use dark colors for code blocks

  <body>
    <div id="map"></div>

    <select id="query-select">
      <option value="" selected>Choose a WHERE clause...</option>
      <option value="UseType = 'Residential'">UseType = 'Residential'</option>
      <option value="UseType = 'Government'">UseType = 'Government'</option>
      <option value="UseType = 'Irrigated Farm'">UseType = 'Irrigated Farm'</option>
      <option value="TaxRateArea = 10853">TaxRateArea = 10853</option>
      <option value="TaxRateArea = 10860">TaxRateArea = 10860</option>
      <option value="TaxRateArea = 08637">TaxRateArea = 08637</option>
      <option value="Roll_LandValue > 1000000">Roll_LandValue &gt; 1000000</option>
      <option value="Roll_LandValue < 1000000">Roll_LandValue &lt; 1000000</option>
    </select>
Expand

Add styling to position the select element in the top right.

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


    #query-select {
      position: absolute;
      top: 20px;
      right: 20px;
      padding: 4px 8px;
      font-size: 16px;
      border-radius: 0;
      /* Causes more uniform appearance across browsers. */
    }

Expand

Add parcel layer

Parcels returned by the query are simple GeoJSON polygons. You will create a Vector layer to display them.

Create a Vector layer and save it to a parcelLayer variable. Add it to the map with map.addLayer.

As you are not passing a style parameter, the default styling for polygons will be used. See the OpenLayers documentation for more details.

Expand
Use dark colors for code blocks
    const basemapId = "arcgis/navigation";
    const basemapURL = `https://basemapstyles-api.arcgis.com/arcgis/rest/services/styles/v2/styles/${basemapId}?token=${accessToken}`;

    const parcelLayer = new ol.layer.Vector();

    olms.apply(map, basemapURL).then((map) => {

      map.addLayer(parcelLayer);

      // Add Esri attribution
      // Learn more in https://esriurl.com/attribution
      const source = map.getLayers().item(0).getSource();
      const poweredByEsriString = "Powered by <a href='https://www.esri.com/en-us/home' target='_blank'>Esri</a> | ";

      const attributionFn = source.getAttributions();
      if (attributionFn) {
        source.setAttributions((ViewStateLayerStateExtent) => {
          return [poweredByEsriString, ...attributionFn(ViewStateLayerStateExtent)];
        });
      } else source.setAttributions(poweredByEsriString);

    });
Expand

Create 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 your function will take a geometry object in 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, create a new Vector source using a GeoJSON feature format, to update your parcelsLayer Vector layer.

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.

Expand
Use dark colors for code blocks
      map.addLayer(parcelLayer);

      // Add Esri attribution
      // Learn more in https://esriurl.com/attribution
      const source = map.getLayers().item(0).getSource();
      const poweredByEsriString = "Powered by <a href='https://www.esri.com/en-us/home' target='_blank'>Esri</a> | ";

      const attributionFn = source.getAttributions();
      if (attributionFn) {
        source.setAttributions((ViewStateLayerStateExtent) => {
          return [poweredByEsriString, ...attributionFn(ViewStateLayerStateExtent)];
        });
      } else source.setAttributions(poweredByEsriString);

    });

    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"]
        })

    }
Expand

Add a response handler. Inside, create a GeoJSON feature format. Use it to read features from the response to a new Vector source.

Expand
Use dark colors for code blocks
    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"]
        })

        .then((response) => {
          const geojson = new ol.format.GeoJSON({
            defaultDataProjection: "EPSG:4326",
            featureProjection: "EPSG:3857"
          });

          let newSource = new ol.source.Vector({
            features: geojson.readFeatures(response),

          });
          parcelLayer.setSource(newSource);
        });

    }
Expand

Add the data attribution for the feature layer source.

Go to the LA County Parcels item.
Scroll down to the Acknowledgments section and copy its value.

Paste the copied value to the attributions property.

Expand
Use dark colors for code blocks
    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"]
        })

        .then((response) => {
          const geojson = new ol.format.GeoJSON({
            defaultDataProjection: "EPSG:4326",
            featureProjection: "EPSG:3857"
          });

          let newSource = new ol.source.Vector({
            features: geojson.readFeatures(response),

            // Attribution text retrieved from https://arcgis.com/home/item.html?id=a6fdf2ee0e454393a53ba32b9838b303
            attributions: ["| County of Los Angeles Office of the Assessor"]

          });
          parcelLayer.setSource(newSource);
        });

    }
Expand

Execute the query

The executeQuery function needs to execute when you select an option from the select control. You achieve this by adding a change event handler. You can access the chosen where clause with the value property of the select element.

You need to calculate the extent of the current map view in latitude and longitude. You can use View.calculateExtent to get the extent, and proj.transformExtent to convert it to the EPSG:4326 spatial reference.

Add a change event handler to the select element. Inside, use View.calculateExtent and ol.proj.transformExtent to calculate the viewport extent. Call executeQuery with the extent and where clause.

Expand
Use dark colors for code blocks
          let newSource = new ol.source.Vector({
            features: geojson.readFeatures(response),

            // Attribution text retrieved from https://arcgis.com/home/item.html?id=a6fdf2ee0e454393a53ba32b9838b303
            attributions: ["| County of Los Angeles Office of the Assessor"]

          });
          parcelLayer.setSource(newSource);
        });

    }

    // Listen for changes
    const select = document.getElementById("query-select");
    select.addEventListener("change", () => {
      const whereClause = select.value;

      const extent3857 = map.getView().calculateExtent(map.getSize());
      const extent4326 = ol.proj.transformExtent(extent3857, "EPSG:3857", "EPSG:4326");
      executeQuery(whereClause, extent4326);
    });

Expand

At the top right, click Run.

When you select a where clause using the select control, 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

The parcels returned from the query contain many attributes, such as land value and land use type. You can make the parcels interactive by showing a pop-up when the user clicks on a parcel. You create a Popup to display parcel attributes. It is a type of Overlay so you add it to the map with map.addOverlay.

Create a Popup and save it to a popup variable. Add it to the map with map.addOverlay.

Expand
Use dark colors for code blocks
      const extent3857 = map.getView().calculateExtent(map.getSize());
      const extent4326 = ol.proj.transformExtent(extent3857, "EPSG:3857", "EPSG:4326");
      executeQuery(whereClause, extent4326);
    });

    const popup = new Popup();
    map.addOverlay(popup);
Expand

Create a map click event handler. Inside, use map.getFeaturesAtPixel to get the clicked parcel, if any. If there is one, use popup.show to display a pop-up containing the parcel's APN, use type, land value and taxation city.

Expand
Use dark colors for code blocks
    const popup = new Popup();
    map.addOverlay(popup);

    map.on("click", (event) => {
      const parcel = map.getFeaturesAtPixel(event.pixel, {
        layerFilter: (l) => l === parcelLayer // don't query layers from the basemap
      })[0];
      if (parcel) {
        const message =
          `<b>Parcel ${parcel.get("APN")}</b>` +
          `<br>Type: ${parcel.get("UseType")} <br>` +
          `Land value: ${parcel.get("Roll_LandValue")} <br>` +
          `Tax Rate City: ${parcel.get("TaxRateCity")}`;
        popup.show(event.coordinate, message);
      } else {
        popup.hide();
      }
Expand

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's attributes.