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How to create a virtual layer in SQLite?
Functions from SQLite and spatial functions from Spatialite can also be used in a virtual layer query. For instance, creating a point layer out of a attribute-only layer can be done with a query similar to: SELECT id, MakePoint (x, y, 4326) as geometry FROM coordinates
Can a computed layer be used in a SpatiaLite view?
[qGIS 3.10.14] Only on computed layer such as virtual or spatialite view: When simply clicking in canvas (or using any other gui/spatial selection method) to select particular feature (s), what gets I have a virtual layer already set up and working, the only thing that could make it better is getting rid of multipart geometries.
What can be used in a virtual layer query?
The underlying engine uses SQLite and Spatialite to operate. It means you can use all of the SQL your local installation of SQLite understands. Functions from SQLite and spatial functions from Spatialite can also be used in a virtual layer query.
What do you mean by virtual layers in QGIS?
A special kind of vector layer allows you to define a layer as the result of an advanced query, using the SQL language on any number of other vector layers that QGIS is able to open. These layers are called virtual layers: they do not carry data by themselves and can be seen as views to other layers.
When to use QGIS expressions in virtual layer?
Functions of QGIS expressionscan also be used in a virtual layer query. To refer the geometry column of a layer, use the name geometry. Contrary to a pure SQL query, all the fields of a virtual layer query must be named. Don’t forget to use the askeyword to name your columns if they are the result of a computation or function call.
How are joins and complex queries created in QGIS?
Joins and complex queries can also be created simply by directly using the names of the layers that are to be joined. The underlying engine uses SQLite and Spatialite to operate. It means you can use all of the SQL your local installation of SQLite understands.
What is the use of indexes in QGIS?
Use of indexes A special kind of vector layer allows you to define a layer as the result of an advanced query, using the SQL language on any number of other vector layers that QGIS is able to open. These layers are called virtual layers: they do not carry data by themselves and can be seen as views to other layers.
How to query a feature layer in ArcGIS?
A feature layer can contain a large number of features stored in ArcGIS. To access a subset of the features, you can execute either a SQL or spatial query, or both at the same time. You can return feature attributes, geometry, or both attributes and geometry for each record.