How does the querytask function in ArcGIS work?

How does the querytask function in ArcGIS work?

The ArcGIS Server REST service URL (usually of a Feature Service Layer or Map Service Layer) for use in a task. Executes a Query against the layer specified in the url. Query information about attachments associated with features from a feature layer specified in the url.

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.

What can you do with querytask in JavaScript?

With QueryTask, you can also obtain the number of features that satisfy the query, the extent of features, related features or records associated with a feature, attachments for features or the featureIds of features.

Executes a Query against an ArcGIS Server map layer. The result is returned as a FeatureSet. If the query is successful, the user-specified callback function is invoked with the result. A FeatureSet contains an array of Graphic features, which can be added to the map using Map.graphics.add ().

What happens when a query is successful in ArcGIS?

If the query is successful, the user-specified callback function is invoked with the result. A FeatureSet contains an array of Graphic features, which can be added to the map using Map.graphics.add (). This array will not be populated if no results are found. Specifies the attributes and spatial filter of the query.

What does execute ( ) do in querytask?

QueryTask.execute () returns a Promise that resolves to a FeatureSet, which contains the features in the layer that satisfy the Query.

How to use the ArcGIS API in JavaScript?

Executes a query operation on a layer resource of a map service exposed by the ArcGIS Server REST API. Search for samples that use this class. new QueryTask (url, options?)

When to return error object in JavaScript querytask?

Specifies the attributes and spatial filter of the query. The function to call when the method has completed. The arguments in the function are the same as the onComplete event. An error object is returned if an error occurs on the Server during task execution.

How to query an ArcGIS class in JavaScript?

The ArcGIS Server REST service URL (usually of a Feature Service Layer or Map Service Layer) for use in a task. The name of the class. The declared class name is formatted as esri.folder.className. Specify the geodatabase version to query.

Which is the most common method in querytask?

The most common method used in this class is execute (), which executes the query as defined in the Query object that is passed as a parameter to the function. QueryTask.execute () returns a Promise that resolves to a FeatureSet, which contains the features in the layer that satisfy the Query.

How to use executequerytask, query and featureset?

In this example, a function named “executeQueryTask” is called after a user types in a population value and clicks the “Get Details” button. The “population” value is plugged into Query.where. The where attribute is one of three filters you can use with Query: Query.where: any valid SQL where statement.

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.

When to use datum transformation in ArcGIS query?

Datum transformation used for projecting geometries in the query results when outSpatialReference is different than the layer’s spatial reference. Requires ArcGIS Server service 10.5 or greater. The name of the class. The declared class name is formatted as esri.folder.className. Specifies a search distance from a given geometry in a spatial query.