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How to query for features in ArcGIS JavaScript?
outStatistics – Querying for statistics will never return features from the layer, only an object with number properties for the requested statistics. returnDistinctValues – Returns the unique values that exist in a field as an array of strings, so no features are returned when this parameter is true.
When to use ArcGIS API for JavaScript 4.0?
Since: ArcGIS API for JavaScript 4.0 This class defines parameters for executing queries for features from a layer or layer view. Once a Query object’s properties are defined, it can then be passed into an executable function, which will return the features in a FeatureSet.
How to query features based on attribute values?
To query features based on attribute values, specify a SQL where clause in the where property. You can optionally use the text property for a LIKE statement. Setting the outFields of the query will limit the attributes returned from the query. This can improve the speed of the query if your app doesn’t require all the attributes for each feature.
What does a featureset do in ArcGIS querytask?
A FeatureSet contains an array of Graphic features, which can be added to the map. This array will not be populated if no results are found. Specifies the attributes and spatial filter of the query.
How to return statistics from a JavaScript query?
Rather than return individual features from a query, you can return statistics for field attributes and expressions. Statistic queries are defined by the outStatistics parameter, which requires an array of StatisticDefinition objects.
How to do a spatial query in JavaScript?
To execute a spatial query, you must set the geometry parameter to a Geometry object and specify a valid spatialRelationship . You can optionally provide a query distance and units to query features against a buffer around the given geometry.
Is it necessary to query multiple layers in a map service?
Occasionally, it is necessary to query multiple layers simultaneously. If the requirement is to query all layers in a map service, then an identify task should be used. Otherwise, it can be useful to use multiple query tasks to query different layers. The potential hangup with this approach is how to know when all queries have finished.
How is a spatial query defined in ArcGIS?
For spatial queries, this parameter defines the spatial relationship to query features in the layer or layer view against the input geometry. This parameter can be either standard SQL92 standard or it can use the native SQL of the underlying datastore native. The zero-based index indicating where to begin retrieving features.