Filter a feature layer with SQL

Learn how to use a SQL query to limit features displayed in a feature layer.

A hosted feature layer can contain a large number of features. To display a subset of the features, you can filter features on the server-side with a definition expression. Definition expressions are different than feature layer queries: they only support a SQL where clause without a geometry (spatial) parameter, and are only used to filter features at the time they are displayed in a map or scene. They cannot be used to get features like a feature layer query.

In this tutorial, you will apply a server-side SQL query with a definitionExpression to filter the LA County Parcels feature layer .

Prerequisites

Steps

Create a new pen

1. To get started, either complete the Display a map tutorial or use this pen.

Set the API key

To access ArcGIS services, you need an API key.

1. Go to your dashboard to get an API key.

2. In CodePen, set the apiKey to your key, so it can be used to access basemap layer and location services.

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   esriConfig.apiKey = "YOUR_API_KEY";
   const map = new Map({
     basemap: "arcgis-topographic" // Basemap layer service
   });

Add modules

1. In the require statement, add the FeatureLayer module.

   More info

   The ArcGIS Maps SDK for JavaScript is available as AMD modules and ES modules, but this tutorial is based on AMD. The AMD require function uses references to determine which modules will be loaded – for example, you can specify "esri/Map" for loading the Map module. After the modules are loaded, they are passed as parameters (e.g. Map) to the callback function where they can be used in your application. It is important to keep the module references and callback parameters in the same order. For more information on the different types of modules, visit the Introduction to Tooling guide topic.

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   <script>
     require([
         "esri/config",
         "esri/Map",
         "esri/views/MapView",
   
         "esri/layers/FeatureLayer"
   
       ], function(esriConfig, Map, MapView, FeatureLayer) {
   

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Create a selector

Use an HTML select element to provide a list of SQL queries for the LA County Parcels feature layer.

1. Create a sqlExpressions array of SQL queries.

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         const view = new MapView({
           container: "viewDiv",
           map: map,
           center: [-118.80543,34.02700], // Longitude, latitude
           zoom: 12
         });
   
         // Create a UI with the filter expressions
         const sqlExpressions = ["Choose a SQL where clause...", "Roll_LandValue < 200000", "TaxRateArea = 10853", "Bedrooms5 > 0", "UseType = 'Residential'", "Roll_RealEstateExemp > 0"];
   

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2. Create a parent selectFilter element and add option elements for each SQL query. Add some css styles to the elements.

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         // Create a UI with the filter expressions
         const sqlExpressions = ["Choose a SQL where clause...", "Roll_LandValue < 200000", "TaxRateArea = 10853", "Bedrooms5 > 0", "UseType = 'Residential'", "Roll_RealEstateExemp > 0"];
   
         // UI
         const selectFilter = document.createElement("select");
         selectFilter.setAttribute("class", "esri-widget esri-select");
         selectFilter.setAttribute("style", "width: 275px; font-family: Avenir Next W00; font-size: 1em;");
   
         sqlExpressions.forEach(function(sql){
           let option = document.createElement("option");
           option.value = sql;
           option.innerHTML = sql;
           selectFilter.appendChild(option);
         });
   
   

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3. Add selectFilter to the top-right corner of the view.

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         sqlExpressions.forEach(function(sql){
           let option = document.createElement("option");
           option.value = sql;
           option.innerHTML = sql;
           selectFilter.appendChild(option);
         });
   
         view.ui.add(selectFilter, "top-right");
   

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4. Verify that the select element is created.

Create a feature layer to filter

Use the FeatureLayer class to access the LA County Parcels feature layer. Since you are performing a server-side query, the feature layer does not need to be added to the map. However, to view the results of the query, the feature layer will be added to the map.

1. Create a featureLayer and set the url property to access the feature layer in the feature service. Set the outFields property to return all attributes on the client and the popupTemplate to display the parcel description and land value. Set the definitionExpression to 1=0 so no features are displayed when the layer is loaded. Add featureLayer to the map.

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         view.ui.add(selectFilter, "top-right");
   
         // Add a feature layer to map with all features visible on client (no filter)
         const featureLayer = new FeatureLayer({
           url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/LA_County_Parcels/FeatureServer/0",
           outFields: ["*"],
           popupTemplate: {
             title: "{UseType}",
             content: "Description: {UseDescription}. Land value: {Roll_LandValue}"
           },
           definitionExpression: "1=0"
         });
         map.add(featureLayer);
   
   

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Apply the SQL expression

The definitionExpression is the SQL where clause. Use the expression to apply a filter and limit features displayed in the map.

1. Create a setFeatureLayerFilter function with an expression parameter. Set the definitionExpression to filter the feature layer with the expression.

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         view.ui.add(selectFilter, "top-right");
   
         // Add a feature layer to map with all features visible on client (no filter)
         const featureLayer = new FeatureLayer({
           url: "https://services3.arcgis.com/GVgbJbqm8hXASVYi/arcgis/rest/services/LA_County_Parcels/FeatureServer/0",
           outFields: ["*"],
           popupTemplate: {
             title: "{UseType}",
             content: "Description: {UseDescription}. Land value: {Roll_LandValue}"
           },
           definitionExpression: "1=0"
         });
         map.add(featureLayer);
   
         // Server-side filter
         function setFeatureLayerFilter(expression) {
           featureLayer.definitionExpression = expression;
         }
   
   

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2. Add an event listener to call the setFeatureLayerFilter function when a SQL where clause is chosen from the selector.

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         // Server-side filter
         function setFeatureLayerFilter(expression) {
           featureLayer.definitionExpression = expression;
         }
   
         // Event listener
         selectFilter.addEventListener('change', function (event) {
           setFeatureLayerFilter(event.target.value);
         });
   

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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 choose a SQL query from the selector that applies a definition expression to the visible extent of the map. Only the features that match are added to the feature layer and displayed in the view.

What's next?

Learn how to use additional API features and ArcGIS services in these tutorials:

• Query a feature layer (SQL)
• Query a feature layer (spatial)
• Import data as a feature layer