How to create a virtual layer in SQL?

How to create a virtual layer in SQL?

For example, if you have a layer called regions, you can create a new virtual layer with an SQL query like SELECT * FROM regions WHERE id < 100 . The SQL query will be executed, whatever the underlying provider of the regions layer is and even if this provider does not directly support SQL queries.

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.

How to merge two attribute tables in a layer?

You can merge them by going to: you can also join two attribute tables in Layer Properties but as mentioned above you’ll need a common field between attribute tables. To eliminate duplicate geometries you can both dissolve the layer by field: Alternatively, I can suggest using a “Virtual Layer” through Layer > Add Layer > Add/Edit Virtual Layer…

How to merge vector interaction and attribute tables?

Currently, I have two attribute tables my vector table and an additional table for vector interaction. I was wondering if I could merge the attribute tables within the software. As I would like to use the ‘delete duplicate geometries’ as some of the data would be reoccurring and would like to delete them without manually doing that.

Can a virtual layer ignore the geometry field?

No geometry: this option forces the virtual layer to ignore any geometry field. The resulting layer is an attribute-only layer. Geometry Column: this option allows to specify the name of the column that is to be used as the geometry of the layer.

Why do I need to define unique identifier in virtual layer?

Defining a unique identifier column allows to speed up the selection of rows by id. No geometry: this option forces the virtual layer to ignore any geometry field.

Can a layer have more than one display filter?

A layer can contain many display filters, but only one display filter is applied to the layer at any time. There are two ways to specify the currently active display filter: By scale—In this mode, each display filter on a layer is associated with a visible scale range.

How does a display filter affect the labeling of a layer?

When a display filter is active, all features in the layer remain in the layer’s attribute table and can be selected, identified, edited, and be available for geoprocessing operations. But, because only visible features are labeled, display filters affect the labeling of a layer.

How to filter feature using openlayer and WFS?

But I’m facing problem when I only want to display the data with certain features aka filtering. I followed filtering tutorial from https://www.giserdqy.com/wp-content/guids/ol-v4.6.5/examples/vector-wfs-getfeature.html and I also have tried using CQL_FILTER but no luck at all

How to configure an aggregate Ethernet ( AE ) interface?

To configure an Aggregate Ethernet (AE) Interface, first configure an Aggregate Ethernet (AE) Interface Group and click the name of the interface you will assign to that group.

How does the virtual layer engine work in QGIS?

With default parameters set, the virtual layer engine will try its best to detect the type of the different columns of the query, including the type of the geometry column if one is present. This is done by introspecting the query when possible or by fetching the first row of the query (LIMIT 1) at last resort.

Which is the main element of the Processing Toolbox?

The Processing Toolbox is the main element of the processing GUI, and the one that you are more likely to use in your daily work. It shows the list of all available algorithms grouped in different blocks called Providers, and custom models and scripts you can add to extend the set of tools.

What is the Processing Toolbox in QGIS?

The Processing Toolboxis the main element of the processing GUI, and the one that you are more likely to use in your daily work. It shows the list of all available algorithmsgrouped in different blocks called Providers, and custom modelsand scriptsyou can add to extend the set of tools.