Class: QgsQueryBuilder

Query Builder for layers.

The query builder allows interactive creation of a SQL for limiting the features displayed in a vector layer. The fields in the table are displayed and sample values (or all values) can be viewed to aid in constructing the query. A test function returns the number of features that will be returned.

Class Hierarchy

Base classes

QgsSubsetStringEditorInterface	Interface for a dialog that can edit subset strings.
QDialog
QWidget
QObject
QPaintDevice

class qgis.gui.QgsQueryBuilder

Bases: QgsSubsetStringEditorInterface

__init__(layer: QgsVectorLayer | None, parent: QWidget | None = None, fl: Qt.WindowFlags | Qt.WindowType = QgsGuiUtils.ModalDialogFlags)

This constructor is used when the query builder is called from the vector layer properties dialog

Parameters:

• layer (Optional[QgsVectorLayer]) – existing vector layer

• parent (Optional[QWidget] = None) – Parent widget

• fl (Union[Qt.WindowFlags, Qt.WindowType] = QgsGuiUtils.ModalDialogFlags) – dialog flags

clear(self)

codeEditorWidget(self) → QgsCodeEditor | None

Returns the code editor widget for the SQL.

Added in version 3.18.

Return type:

Optional[QgsCodeEditor]

loadQuery(self)

Load query from the XML file

Added in version 3.16.

static loadQueryFromFile(subset: str | None) → bool

Load query from the XML file

Added in version 3.26.

Parameters:

subset (Optional[str])

Return type:

bool

saveQuery(self)

Save query to the XML file

Added in version 3.16.

static saveQueryToFile(subset: str | None) → bool

Save query to the XML file

Added in version 3.26.

Parameters:

subset (Optional[str])

Return type:

bool

setDatasourceDescription(self, uri: str | None)

Parameters:

uri (Optional[str])

setSql(self, sqlStatement: str | None)

Set the sql statement to display in the dialog.

Parameters:

sqlStatement (Optional[str])

sql(self) → str

Returns the sql statement entered in the dialog.

Return type:

str

virtual test(self)

The default implementation tests that the constructed sql statement to see if the vector layer data provider likes it. The number of rows that would be returned is displayed in a message box. The test uses a “select count(*) from …” query to test the SQL statement.