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QSqlRelationalTableModel Class Reference
^{[QtSql module]}

The QSqlRelationalTableModel class provides an editable data model for a single database table, with foreign key support. More...

Inherits QSqlTableModel.

Methods

• __init__ (self, QObject parent = None, QSqlDatabase db = QSqlDatabase())
• clear (self)
• QVariant data (self, QModelIndex item, int role = Qt.DisplayRole)
• bool insertRowIntoTable (self, QSqlRecord values)
• QString orderByClause (self)
• QSqlRelation relation (self, int column)
• QSqlTableModel relationModel (self, int column)
• bool removeColumns (self, int column, int count, QModelIndex parent = QModelIndex())
• revertRow (self, int row)
• bool select (self)
• QString selectStatement (self)
• bool setData (self, QModelIndex item, QVariant value, int role = Qt.EditRole)
• setRelation (self, int column, QSqlRelation relation)
• setTable (self, QString tableName)
• bool updateRowInTable (self, int row, QSqlRecord values)

QSqlRelationalTableModel acts like QSqlTableModel, but allows columns to be set as foreign keys into other database tables.

The screenshot on the left shows a plain QSqlTableModel in a QTableView. Foreign keys (city and country) aren't resolved to human-readable values. The screenshot on the right shows a QSqlRelationalTableModel, with foreign keys resolved into human-readable text strings.

The following code snippet shows how the QSqlRelationalTableModel was set up:

     model->setTable("employee");

     model->setRelation(2, QSqlRelation("city", "id", "name"));
     model->setRelation(3, QSqlRelation("country", "id", "name"));

The setRelation() function calls establish a relationship between two tables. The first call specifies that column 2 in table employee is a foreign key that maps with field id of table city, and that the view should present the city's name field to the user. The second call does something similar with column 3.

If you use a read-write QSqlRelationalTableModel, you probably want to use QSqlRelationalDelegate on the view. Unlike the default delegate, QSqlRelationalDelegate provides a combobox for fields that are foreign keys into other tables. To use the class, simply call QAbstractItemView.setItemDelegate() on the view with an instance of QSqlRelationalDelegate:

     QTableView *view = new QTableView;
     view->setModel(model);
     view->setItemDelegate(new QSqlRelationalDelegate(view));

The sql/relationaltablemodel example illustrates how to use QSqlRelationalTableModel in conjunction with QSqlRelationalDelegate to provide tables with foreigh key support.

Notes:

• The table must have a primary key declared.
• The table's primary key may not contain a relation to another table.
• If a relational table contains keys that refer to non-existent rows in the referenced table, the rows containing the invalid keys will not be exposed through the model. The user or the database is responsible for keeping referential integrity.

See also QSqlRelation, QSqlRelationalDelegate, and Relational Table Model Example.

Method Documentation

QSqlRelationalTableModel.__init__ (self, QObject parent = None, QSqlDatabase db = QSqlDatabase())

The parent argument, if not None, causes self to be owned by Qt instead of PyQt.

Creates an empty QSqlRelationalTableModel and sets the parent to parent and the database connection to db. If db is not valid, the default database connection will be used.

QSqlRelationalTableModel.clear (self)

QVariant QSqlRelationalTableModel.data (self, QModelIndex item, int role = Qt.DisplayRole)

bool QSqlRelationalTableModel.insertRowIntoTable (self, QSqlRecord values)

QString QSqlRelationalTableModel.orderByClause (self)

QSqlRelation QSqlRelationalTableModel.relation (self, int column)

Returns the relation for the column column, or an invalid relation if no relation is set.

See also setRelation() and QSqlRelation.isValid().

QSqlTableModel QSqlRelationalTableModel.relationModel (self, int column)

Returns a QSqlTableModel object for accessing the table for which column is a foreign key, or 0 if there is no relation for the given column.

The returned object is owned by the QSqlRelationalTableModel.

See also setRelation() and relation().

bool QSqlRelationalTableModel.removeColumns (self, int column, int count, QModelIndex parent = QModelIndex())

QSqlRelationalTableModel.revertRow (self, int row)

bool QSqlRelationalTableModel.select (self)

QString QSqlRelationalTableModel.selectStatement (self)

bool QSqlRelationalTableModel.setData (self, QModelIndex item, QVariant value, int role = Qt.EditRole)

Sets the data for the role in the item with the specified index to the value given. Depending on the edit strategy, the value might be applied to the database at once, or it may be cached in the model.

Returns true if the value could be set, or false on error (for example, if index is out of bounds).

For relational columns, value must be the index, not the display value.

Reimplemented from QAbstractItemModel.

See also editStrategy(), data(), submit(), and revertRow().

QSqlRelationalTableModel.setRelation (self, int column, QSqlRelation relation)

Lets the specified column be a foreign index specified by relation.

Example:

     model->setTable("employee");

     model->setRelation(2, QSqlRelation("city", "id", "name"));

The setRelation() call specifies that column 2 in table employee is a foreign key that maps with field id of table city, and that the view should present the city's name field to the user.

Note: The table's primary key may not contain a relation to another table.

See also relation().

QSqlRelationalTableModel.setTable (self, QString tableName)

bool QSqlRelationalTableModel.updateRowInTable (self, int row, QSqlRecord values)