Opening Data

As part of an Open Source Software ecosystem, QGIS is built upon different libraries that, combined with its own providers, offer capabilities to read and often write a lot of formats:

• Vector data formats include ESRI formats (Shapefile, Geodatabase…), MapInfo and MicroStation file formats, AutoCAD DWG/DXF, GeoPackage, GeoJSON, GRASS, GPX, KML, Comma Separated Values, and many more… Read the complete list of OGR vector supported formats.

• Raster data formats include ArcInfo Binary Grid, ArcInfo ASCII Grid, JPEG, GeoTIFF, ERDAS IMAGINE, MBTiles, R or Idrisi rasters, ASCII Gridded XYZ, GDAL Virtual, SRTM, Sentinel Data, and many more… Read the complete list of raster supported formats.

• Database formats include PostgreSQL/PostGIS, SQLite/SpatiaLite, Oracle, DB2 or MSSQL Spatial, MySQL…

• Support of web data services (WM(T)S, WFS, WCS, CSW, ArcGIS Servers…) is also handled by QGIS providers (see QGIS as OGC Data Client).

• You can also read supported files from archived folders and use QGIS native formats such as virtual and memory layers.

As of the date of this document, more than 80 vector and 140 raster formats are supported by the GDAL/OGR and QGIS native providers.

Poznámka

Not all of the listed formats may work in QGIS for various reasons. For example, some require external proprietary libraries, or the GDAL/OGR installation of your OS may not have been built to support the format you want to use. To see the list of available formats, run the command line ogrinfo --formats (for vector) and gdalinfo --formats (for raster), or check Settings ‣ Options ‣ GDAL menu (for raster) in QGIS.

In QGIS, depending on the data format, there are different tools to open it, mainly available in the Layer ‣ Add Layer ‣ menu or from the Manage Layers toolbar (enabled through View ‣ Toolbars menu). However, all these tools point to a unique dialog, the Data Source Manager dialog that you can directly open with the ^{Open Data Source Manager} button available on the Data Source Manager Toolbar or by pressing Ctrl+L. Indeed, the Data Source Manager dialog offers a unified interface to open vector or raster file-based data as well as databases or web services supported by QGIS. It can be set modal or not with the Modeless data source manager dialog in Settings ‣ Options ‣ General menu.

QGIS Data Source Manager dialog

Beside this main entry point, you also have the DB Manager plugin that offers advanced capabilities to analyze and manipulate connected databases. More information on DB Manager capabilities are exposed in DB Manager Plugin.

There are also many other tools, native or third-party plugins, that help you open dedicated data formats.

This chapter will describe only the tools provided by default in QGIS to load data. It will mainly focus on the Data Source Manager dialog but more than describing each tab, it will also explore the tools based on the data provider or format specificities.

The Browser Panel

The Browser is one of the main ways to quickly and easily add your data to projects. It’s available as:

• a Data Source Manager tab, enabled pressing the ^{Open Data Source Manager} button (Ctrl+L);

• as a QGIS panel you can open from the menu View ‣ Panels (or Settings ‣ Panels) or by pressing Ctrl+2.

In both cases, the Browser helps you navigate in your file system and manage geodata, regardless the type of layer (raster, vector, table), or the datasource format (plain or compressed files, database, web services).

The context menu for an element in the Browser panel is opened by right-clicking on it.

For file system directory entries, the context menu offers the following:

• Add as a Favorite

• Properties…

• Hide from Browser

• Fast Scan this Directory

• New Directory…

• Open Directory

Favourites, can also be removed and renamed:

• Rename favourite…

• Remove favourite

For leaf entries that can act as layers in the project, the context menu will have a selection of entries. For example, for non-database, non-service-based vector, raster and mesh data sources:

• Add Selected Layer(s) to Canvas

• Properties…

• Delete File „<name of file>“…

In the Layer properties entry, you will find (similar to what you will find in the vector and raster layer properties once the layers have been added to the project):

• Metadata for the layer. Metadata groups: Information from provider (if possible, Path will be a hyperlink to the source), Identification, Extent, Access, Fields (for vector layers), Bands (for raster layers), Contacts, Links (for vector layers), References (for raster layers), History.

• A Preview panel

• The attribute table for vector sources (in the Attributes panel).

To add a layer to the project using the Browser:

1. Enable the Browser as described above. A browser tree with your file system, databases and web services is displayed. You may need to connect databases and web services before they appear (see dedicated sections).

2. Find the layer in the list.

3. Use the context menu, double-click its name, or drag-and-drop it into the map canvas. Your layer is now added to the Layers panel and can be viewed on the map canvas.

   Tip

   Open a QGIS project directly from the browser

   You can also open a QGIS project directly from the Browser panel by double-clicking its name or by drag-and-drop into the map canvas.

Once a file is loaded, you can zoom around it using the map navigation tools. To change the style of a layer, open the Layer Properties dialog by double clicking on the layer name or by right-clicking on the name in the legend and choosing Properties from the context menu. See section Symbology Properties for more information on setting symbology of vector layers.

At the top of the Browser panel, you find some icons that help you to:

• ^{Add Selected Layers}: you can also add data into the map canvas by selecting Add selected layer(s) from the layer’s context menu;

• ^Refresh the browser tree;

• ^{Filter Browser} to search for specific data. Enter a search word or wildcard and the browser will filter the tree to only show paths to matching DB tables, filenames or folders – other data or folders won’t be displayed. See the Browser Panel(2) example on the figure_browser_panels. The comparison can be case-sensitive or not. It can also be set to:

  • normal: return any item containing the search text;

  • using wildcard(s): fine tune the search using ? and/or * characters to specify the position of the search text;

  • using a regular expression.

• ^{Collapse All} the whole tree;

• ^{Enable/disable properties widget}: when toggled on, a new widget is added at the bottom of the panel showing, if applicable, metadatas of the selected item.

Right-click an item in the browser tree helps you to:

• in case of file or table, display its metadata or open it in your project. Tables can even be renamed, deleted or truncated;

• in case of folder, bookmark it into your favourites, hide it from the browser tree. Hidden folders can be managed from the Settings ‣ Options ‣ Data Sources tab;

• create connection to databases or web servers;

• refresh, rename or delete schema.

You can also import files into databases or copy tables from one schema/database to another one with a simple drag-and-drop. There is a second browser panel available to avoid long scrolling while dragging. Just select the file and drag-and-drop from one panel to the other.

QGIS Browser panels side-by-side

Tip

Add layers to QGIS by simple drag-and-drop from your OS file browser

You can also add file(s) to the project by drag-and-dropping them from your operating system file browser to the Layers Panel or the map canvas.

The DB Manager

The DB Manager Plugin is another one of the main and native tools to integrate and manage spatial database formats supported by QGIS (PostGIS, SpatiaLite, GeoPackage, Oracle Spatial, MSSQL, DB2, Virtual layers) in one user interface. It can be activated from the Plugins ‣ Manage and Install Plugins… menu.

The ^{DB Manager} Plugin provides several features:

• connect to databases and display its structure and contents;

• preview tables of databases;

• add layers to map canvas, either by double-click or drag-and-drop;

• add layers to a database from the QGIS Browser or from another database;

• create and add output of SQL queries to the map canvas;

• create virtual layers.

More information on DB Manager capabilities are exposed in DB Manager Plugin.

DB Manager dialog

Provider-based loading tools

Beside Browser Panel and DB Manager, the main tools provided by QGIS to add layers regardless the format, you’ll also find tools that are specific to data providers.

Poznámka

Some external plugins also propose tools to open specific format files in QGIS.

Loading a layer from a file

To load a layer from a file, you can:

• for vector data (like Shapefile, Mapinfo or dxf layer), click on ^{Add Vector Layer} toolbar button, select the Layer ‣ Add Layer ‣ Add Vector Layer menu option or press Ctrl+Shift+V. This will bring up a new window (see figure_vector_add) from which you can check File and click on Browse. You can also specify the encoding for the file if desired.

  

  Add Vector Layer Dialog

• for raster layers, click on the ^{Add Raster Layer} icon, select the Layer ‣ Add Layer ‣ Add Raster Layer menu option or type Ctrl+Shift+R.

That will bring up a standard open file dialog (see figure_vector_open), which allows you to navigate the file system and load a shapefile, a geotiff or other supported data source. The selection box Filter allows you to preselect some supported file formats. Only the formats that have been well tested appear in the list. Other untested formats can be loaded by selecting All files (*.*).

Open an OGR Supported Vector Layer Dialog

Selecting a file from the list and clicking Open loads it into QGIS. More than one layer can be loaded at the same time by holding down the Ctrl or Shift key and clicking on multiple items in the dialog. Figure_vector_loaded shows QGIS after loading the alaska.shp file.

QGIS with Shapefile of Alaska loaded

Poznámka

Because some formats like MapInfo (e.g., .tab) or Autocad (.dxf) allow mixing different types of geometry in a single file, loading such format in QGIS opens a dialog to select geometries to use in order to have one geometry per layer.

Using the ^{Add Vector Layer} tool:

• You can also load specific formats like ArcInfo Binary Coverage, UK. National Transfer Format, as well as the raw TIGER format of the US Census Bureau or OpenfileGDB. To do that, you’d need to select Directory as Source type. In this case a directory can be selected in the dialog after pressing Browse.

• With the Database source type you can select an existing database connection or create one to the selected database type. Available database types are ODBC, OGDI Vectors, Esri Personal Geodatabase, MySQL as well as PostgreSQL or MSSQL.

  Pressing the New button opens the Create a New OGR Database Connection dialog whose parameters are among the ones you can find in Creating a stored Connection. Pressing Open you can select from the available tables for example of the PostGIS enabled database.

• The last source type, Protocol, enables to open data from the web using for example GeoJSON or CouchDB format. After selecting the type you have to fill URI of the source.

Tip

Load layers and projects from mounted external drives on macOS

On macOS, portable drives that are mounted beside the primary hard drive do not show up as expected under File ‣ Open…. We are working on a more macOS-native open/save dialog to fix this. As a workaround, you can type /Volumes in the File name box and press Enter. Then you can navigate to external drives and network mounts.

Importing a delimited text file

Delimited text file (e.g. .csv, .txt) can be loaded in QGIS using the tools described above. However, loaded this way, it’ll show up like a simple table data. Sometimes, delimited text files can contain geometric data you’d want to visualize; this is what the Add Delimited Text Layer is designed for.

Click the ^{Open Data Source Manager} icon to open the Data Source Manager dialog and enable the Delimited Text tab, as shown in figure_delimited_text.

Delimited Text Dialog

First, select the file to import (e.g., qgis_sample_data/csv/elevp.csv) by clicking on the Browse button. In the Layer name field, provide the name to use for the layer in the project (e.g., Elevation).

File format

Once the file is selected, QGIS attempts to parse the file with the most recently used delimiter, trying to identify fields and rows. To enable QGIS to properly parse the file, it is important to select the correct delimiter. You can specify a delimiter by activating:

• CSV (comma separated values) to use the comma character;

• Custom delimiters, choosing among some predefined delimiters like comma, space, tab, semicolon…;

• or Regular expression delimiter and entering text into the Expression field. For example, to change the delimiter to tab, use \t (this is a regular expression for the tab character).

Records and fields

Other than settings to identify rows and fields in the data, some convenient options can be used to tweak the data recognition:

• Number of header lines to discard: convenient when you want to avoid some lines to show in the import, either because those are blank lines or with another formatting.

• First records has field names: values in the first row of data are used as field names, otherwise QGIS adds a fields row of a type field_1, field_2…

• Detect field types: automatically recognizes the field type. If unchecked then all attributes are treated as text fields.

• Decimal separator is comma: if necessary, you can force a comma to be the decimal separator.

• Trim fields: allows you to trim leading and trailing spaces from fields.

• Discard empty fields.

As you set the parser properties, a sample data preview updates at the bottom of the dialog.

Geometry definition

Once the file is parsed, set Geometry definition to

• Point coordinates and provide the X field and Y field if the layer is of point geometry type and contain such coordinate fields. If the coordinates are defined as degrees/minutes/seconds, activate the DMS coordinates checkbox;

• Well known text (WKT) option if the spatial information is represented by WKT: select the Geometry field containing the WKT definition and choose the approriate Geometry field or let QGIS auto-detect it;

• If the file contains non-spatial data, activate No geometry (attribute only table) and it will be loaded as an ordinary table.

Besides the features geometry information, you can also set the layer’s Geometry CRS using the ^{Select CRS} widget.

Layer settings

Additionally, you can enable:

• Use spatial index to improve the performance of displaying and spatially selecting features;

• Use subset index to improve performance of subset filters (when defined in the layer properties);

• Watch file to watch for changes to the file by other applications while QGIS is running.

At the end, click OK to add the layer to the map. In our example, a point layer named Elevation is added to the project and behaves like any other map layer in QGIS. However, this layer is the result of a query on the .csv source layer (hence, linked to it) and would require to be saved in order to get a spatial layer on disk.

Importing a DXF or DWG file

DXF and DWG files can be added to QGIS by simple drag-and-drop from the common Browser Panel. You’ll be prompted to select the sublayers you’d like to add to the project. Layers are added with random style properties.

Poznámka

DXF files containing several geometry types (point, line and/or polygon), the name of the layer will be made from <filename.dxf> entities <geometry type>.

To keep the dxf/dwg file structure and its symbology in QGIS, you may want to use the dedicated Project ‣ Import/Export ‣ Import Layers from DWG/DXF… tool which allows you to:

1. import elements from the drawing file into a GeoPackage database.

2. and add to the project any of the imported elements.

In the DWG/DXF Import dialog, to first import the drawing file contents:

1. Input the location of the Target package, i.e. the new GeoPackage file that will store the data. If an existing file is provided, then it will be overwritten.

2. Specify the coordinate reference system of the data in the drawing file.

3. Check Expand block references to import the blocks in the drawing file as normal elements.

4. Check Use curves to promote the imported layers to a curved geometry type.

5. Use the Import button to select the DWG/DXF file to use (one per geopackage). The GeoPackage database will be automatically populated with the drawing file content. Depending on the size of the *CAD file, this could take some time.

After the .dwg or .dxf data is imported into the GeoPackage database the frame in the lower half of the dialog is populated with the list of layers from the imported file. There you can select which layers to add to the QGIS project:

1. At the top, set a Group name to group the drawing files in the project.

2. Check layers to show: Each selected layer is added to an ad hoc group which contains vector layers for the point, line, label and area features of the drawing layer. The style of each layer is setup so that it resembles the look it originally had in *CAD.

3. Check whether layer should be visible at opening.

4. Alternatively using the Merge layers option places all layers in a single group.

5. Press OK to open the layers in QGIS.

Import dialog for DWG/DXF files

Importing OpenStreetMap Vectors

In recent years, the OpenStreetMap project has gained popularity because in many countries no free geodata such as digital road maps are available. The objective of the OSM project is to create a free editable map of the world from GPS data, aerial photography or local knowledge. To support this objective, QGIS provides support for OSM data.

Using the Browser Panel, you can load a .osm file to the map canvas, in which case you’ll get a dialog to select sublayers based on the geometry type. The loaded layers will contain all the data of that geometry type in the file and keep the osm file data structure.

SpatiaLite Layers

The first time you load data from a SpatiaLite database, begin by:

• clicking on the ^{Add SpatiaLite Layer} toolbar button;

• selecting the Add SpatiaLite Layer… option from the Layer ‣ Add Layer menu;

• or by typing Ctrl+Shift+L.

This will bring up a window that will allow you either to connect to a SpatiaLite database already known to QGIS, which you can choose from the drop-down menu, or to define a new connection to a new database. To define a new connection, click on New and use the file browser to point to your SpatiaLite database, which is a file with a .sqlite extension.

QGIS also supports editable views in SpatiaLite.

GPS

Loading GPS data in QGIS can be done using the core plugin: GPS Tools. Instructions are described in Section GPS Plugin.

GRASS

Working with GRASS vector data is described in Section GRASS GIS Integration.

Database related tools

Creating a stored Connection

In order to read and write tables from the many database formats QGIS supports you’ll need to create a connection to that database. While QGIS Browser Panel is the simplest and recommanded way to connect and use databases, QGIS provides other tools to connect to each of them and load their tables:

• Add PostGIS Layer… or by typing Ctrl+Shift+D;

• Add MSSQL Spatial Layer or by typing Ctrl+Shift+M;

• Add Oracle Spatial Layer… or by typing Ctrl+Shift+O;

• Add DB2 Spatial Layer… or by typing Ctrl+Shift+2.

These tools are accessible either from the Manage Layers Toolbar or the Layer ‣ Add Layer ‣ menu. Connecting to SpatiaLite database is described at SpatiaLite Layers.

Tip

Create connection to database from the QGIS Browser Panel

Select the corresponding database format in the Browser tree, right-click and choose connect will provide you with the database connection dialog.

Most of the connection dialogs follow a common basis that will be described below using the PostGreSQL database tool as example. For additional settings specific to other providers, you can find corresponding description at:

• Connecting to MSSQL Spatial;

• Connecting to Oracle Spatial;

• Connecting to DB2 Spatial.

The first time you use a PostGIS data source, you must create a connection to a database that contains the data. Begin by clicking the appropriate button as exposed above, opening an Add PostGIS Table(s) dialog (see figure_add_postgis_tables). To access the connection manager, click on the New button to display the Create a New PostGIS Connection dialog.

Create a New PostGIS Connection Dialog

The parameters required for a PostGIS connection are exposed below. For the other database types, see their differences at Particular Connection requirements.

• Name: A name for this connection. It can be the same as Database.

• Service: Service parameter to be used alternatively to hostname/port (and potentially database). This can be defined in pg_service.conf. Check the PostgreSQL Service connection file section for more details.

• Host: Name of the database host. This must be a resolvable host name such as would be used to open a TCP/IP connection or ping the host. If the database is on the same computer as QGIS, simply enter localhost here.

• Port: Port number the PostgreSQL database server listens on. The default port for PostGIS is 5432.

• Database: Name of the database.

• SSL mode: SSL encryption setup. The following options are available:

  • Prefer (the default): I don’t care about encryption, but I wish to pay the overhead of encryption if the server supports it.

  • Require: I want my data to be encrypted, and I accept the overhead. I trust that the network will make sure I always connect to the server I want.

  • Verify CA: I want my data encrypted, and I accept the overhead. I want to be sure that I connect to a server that I trust.

  • Verify Full: I want my data encrypted, and I accept the overhead. I want to be sure that I connect to a server I trust, and that it’s the one I specify.

  • Allow: I don’t care about security, but I will pay the overhead of encryption if the server insists on it.

  • Disable: I don’t care about security, and I don’t want to pay the overhead of encryption.

• Authentication, basic.

• Username: User name used to log in to the database.

• Password: Password used with Username to connect to the database.

  You can save any or both of the username and password parameters, in which case they will be used by default each time you need to connect to this database. If not saved, you’ll be prompted to fill the missing credentials to connect to the database in next QGIS sessions; meanwhile the connection parameters you entered are stored in a temporary internal cache and returned whenever a username/password for the same database is requested, until you close the current QGIS process.

  Varování

  QGIS User Settings and Security

  In the Authentication tab, saving username and password will keep unprotected credentials in the connection configuration. Those credentials will be visible if, for instance, you shared the project file with someone. Therefore, it’s advisable to save your credentials in a Authentication configuration instead (Configurations tab - See Authentication System for more details) or in a service connection file (see PostgreSQL Service connection file for example).

Optionally, depending on the type of database, you can activate the following checkboxes:

• Only show layers in the layer registries

• Don’t resolve type of unrestricted columns (GEOMETRY)

• Only look in the ‚public‘ schema

• Also list tables with no geometry

• Use estimated table metadata

• Allow saving/loading QGIS projects in the database: more details here

Tip

Use estimated table metadata to speed up operations

When initializing layers, various queries may be needed to establish the characteristics of the geometries stored in the database table. When the Use estimated table metadata option is checked, these queries examine only a sample of the rows and use the table statistics, rather than the entire table. This can drastically speed up operations on large datasets, but may result in incorrect characterization of layers (eg. the feature count of filtered layers will not be accurately determined) and may even cause strange behaviour in case columns that are supposed to be unique actually are not.

Once all parameters and options are set, you can test the connection by clicking on the Test Connection button or apply it hitting OK. From the Add PostGIS Table(s), click now on Connect and the dialog is filled with tables from the selected database (as shown in figure_add_postgis_tables).

Particular Connection requirements

Because of database type particularities, provided options are all the same for all the databases. Below are exposed these connection specificities.

PostgreSQL Service connection file

The service connection file allows PostgreSQL connection parameters to be associated with a single service name. That service name can then be specified by a client and the associated settings will be used.

It’s called .pg_service.conf under *nix systems (GNU/Linux, macOS etc.) and pg_service.conf on Windows.

The service file looks like:

[water_service]
host=192.168.0.45
port=5433
dbname=gisdb
user=paul
password=paulspass

[wastewater_service]
host=dbserver.com
dbname=water
user=waterpass

Poznámka

There are two services in the above example: water_service and wastewater_service. You can use these to connect from QGIS, pgAdmin etc. by specifying only the name of the service you want to connect to (without the enclosing brackets). If you want to use the service with psql you need to do something like export PGSERVICE=water_service before doing your psql commands.

You can find all the parameters here

Poznámka

If you don’t want to save the passwords in the service file you can use the .pg_pass option.

On *nix operating systems (GNU/Linux, macOS etc.) you can save the .pg_service.conf file in the user’s home directory and the PostgreSQL clients will automatically be aware of it. For example, if the logged user is web, .pg_service.conf should be saved in the /home/web/ directory in order to directly work (without specifying any other environment variables).

You can specify the location of the service file by creating a PGSERVICEFILE environment variable (e.g. run the export PGSERVICEFILE=/home/web/.pg_service.conf command under your *nix OS to temporarily set the PGSERVICEFILE variable)

You can also make the service file available system-wide (all users) either by placing the .pg_service.conf file at pg_config --sysconfdir or by adding the PGSYSCONFDIR environment variable to specify the directory containing the service file. If service definitions with the same name exist in the user and the system file, the user file takes precedence.

Varování

There are some caveats under Windows:

• The service file should be saved as pg_service.conf and not as .pg_service.conf.

• The service file should be saved in Unix format in order to work. One way to do it is to open it with Notepad++ and Edit ‣ EOL Conversion ‣ UNIX Format ‣ File save.

• You can add environmental variables in various ways; a tested one, known to work reliably, is Control Panel ‣ System and Security ‣ System ‣ Advanced system settings ‣ Environment Variables adding PGSERVICEFILE and the path of the type C:\Users\John\pg_service.conf

• After adding an environment variable you may also need to restart the computer.

Connecting to Oracle Spatial

The spatial features in Oracle Spatial aid users in managing geographic and location data in a native type within an Oracle database. In addition to some of the options in Creating a stored Connection, the connection dialog proposes:

• Database: SID or SERVICE_NAME of the Oracle instance;

• Port: Port number the Oracle database server listens on. The default port is 1521;

• Workspace: Workspace to switch to.

Optionally, you can activate following checkboxes:

• Only look in metadata table: restricts the displayed tables to those that are in the all_sdo_geom_metadata view. This can speed up the initial display of spatial tables.

• Only look for user’s tables: when searching for spatial tables, restricts the search to tables that are owned by the user.

• Also list tables with no geometry: indicates that tables without geometry should also be listed by default.

• Use estimated table statistics for the layer metadata: when the layer is set up, various metadata are required for the Oracle table. This includes information such as the table row count, geometry type and spatial extents of the data in the geometry column. If the table contains a large number of rows, determining this metadata can be time-consuming. By activating this option, the following fast table metadata operations are done: Row count is determined from all_tables.num_rows. Table extents are always determined with the SDO_TUNE.EXTENTS_OF function, even if a layer filter is applied. Table geometry is determined from the first 100 non-null geometry rows in the table.

• Only existing geometry types: only lists the existing geometry types and don’t offer to add others.

• Include additional geometry attributes.

Tip

Oracle Spatial Layers

Normally, an Oracle Spatial layer is defined by an entry in the USER_SDO_METADATA table.

To ensure that selection tools work correctly, it is recommended that your tables have a primary key.

Connecting to DB2 Spatial

In addition to some of the options described in Creating a stored Connection, the connection to a DB2 database (see DB2 Spatial Layers for more information) can be specified using either a Service/DSN name defined to ODBC or using the driver, host and port information.

An ODBC Service/DSN connection requires the service name defined to ODBC.

A driver/host/port connection requires:

• Driver: Name of the DB2 driver. Typically this would be IBM DB2 ODBC DRIVER.

• DB2 Host: Name of the database host. This must be a resolvable host name such as would be used to open a TCP/IP connection or ping the host. If the database is on the same computer as QGIS, simply enter localhost here.

• DB2 Port: Port number the DB2 database server listens on. The default DB2 LUW port is 50000. The default DB2 z/OS port is 446.

Tip

DB2 Spatial Layers

A DB2 Spatial layer is defined by a row in the DB2GSE.ST_GEOMETRY_COLUMNS view.

Poznámka

In order to work effectively with DB2 spatial tables in QGIS, it is important that tables have an INTEGER or BIGINT column defined as PRIMARY KEY and if new features are going to be added, this column should also have the GENERATED characteristic.

It is also helpful for the spatial column to be registered with a specific spatial reference identifier (most often 4326 for WGS84 coordinates). A spatial column can be registered by calling the ST_Register_Spatial_Column stored procedure.

Connecting to MSSQL Spatial

In addition to some of the options in Creating a stored Connection, creating a new MSSQL connection dialog proposes you to fill a Provider/DSN name. You can also display available databases.

Loading a Database Layer

Once you have one or more connections defined to a database (see section Creating a stored Connection), you can load layers from it. Of course, this requires having available data. See e.g. section Importing Data into PostgreSQL for a discussion on importing data into a PostGIS database.

To load a layer from a database, you can perform the following steps:

1. Open the „Add <database> table(s)“ dialog (see Creating a stored Connection).

2. Choose the connection from the drop-down list and click Connect.

3. Select or unselect Also list tables with no geometry.

4. Optionally, use some Search Options to reduce the list of tables to those matching your search. You can also set this option before you hit the Connect button, speeding this way the database fetching.

5. Find the layer(s) you wish to add in the list of available layers.

6. Select it by clicking on it. You can select multiple layers by holding down the Shift key while clicking.

7. If applicable, use the Set Filter button (or double-click the layer) to start the Query Builder dialog (See section Query Builder) and define which features to load from the selected layer. The filter expression appears in the sql column. This restriction can be removed or edited in the Layer Properties ‣ General ‣ Provider Feature Filter frame.

8. The checkbox in the Select at id column that is activated by default gets the features ids without the attributes and speeds in most cases the data loading.

9. Click on the Add button to add the layer to the map.

Add PostGIS Table(s) Dialog

Tip

Use the Browser Panel to speed up loading of database table(s)

Adding DB tables from their ad hoc tab of the Data Source Manager dialog to QGIS may sometimes be time consuming as QGIS fetches statistics and properties (e.g. geometry type and field, CRS, number of features) of each table beforehand. To avoid this, once the connection is set, it’s better to use the Browser Panel or the DB Manager to drag and drop the database tables in the map canvas.

QGIS Custom formats

QGIS proposes two custom formats you can load in the application using their own loading tool:

• Temporary Scratch Layer: a memory layer that is bound to the project it’s opened with (see Creating a new Temporary Scratch Layer for more information)

• Virtual Layers: a layer resulting from a query on other layer(s) (see Creating virtual layers for more information)

QLR - QGIS Layer Definition File

Layer definitions can be saved as a Layer Definition File (QLR - .qlr) using Export ‣ Save As Layer Definition File… in the layer context menu.

The QLR format makes it possible to share „complete“ QGIS layers with other QGIS users. QLR files contain links to the data sources and all the QGIS style information necessary to style the layer.

QLR files are shown in the Browser Panel and can be used to add layers (with their saved styles) to the Layers Panel. You can also drag and drop QLR files from the system file manager into the map canvas.

Connecting to web services

With QGIS you can have access to different types of OGC web services (WM(T)S, WFS(-T), CSW …). Thanks to QGIS Server, you can also publish these services. Description of these capabilities and how-to are provided in chapter Working with OGC Data.