QSqlQueryModel Class Reference
[QtSql module]

Detailed Description

The QSqlQueryModel class provides a read-only data model for SQL result sets.

QSqlQueryModel is a high-level interface for executing SQL statements and traversing the result set. It is built on top of the lower-level QSqlQuery and can be used to provide data to view classes such as QTableView. For example:

     QSqlQueryModel *model = new QSqlQueryModel;
     model->setQuery("SELECT name, salary FROM employee");
     model->setHeaderData(0, Qt::Horizontal, tr("Name"));
     model->setHeaderData(1, Qt::Horizontal, tr("Salary"));

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

We set the model's query, then we set up the labels displayed in the view header.

QSqlQueryModel can also be used to access a database programmatically, without binding it to a view:

     QSqlQueryModel model;
     model.setQuery("SELECT * FROM employee");
     int salary = model.record(4).value("salary").toInt();

The code snippet above extracts the salary field from record 4 in the result set of the query SELECT * from employee. Assuming that salary is column 2, we can rewrite the last line as follows:

     int salary = model.data(model.index(4, 2)).toInt();

The model is read-only by default. To make it read-write, you must subclass it and reimplement setData() and flags(). Another option is to use QSqlTableModel, which provides a read-write model based on a single database table.

The sql/querymodel example illustrates how to use QSqlQueryModel to display the result of a query. It also shows how to subclass QSqlQueryModel to customize the contents of the data before showing it to the user, and how to create a read-write model based on QSqlQueryModel.

If the database doesn't return the amount of selected rows in a query, the model will fetch rows incrementally. See fetchMore() for more information.

See also QSqlTableModel, QSqlRelationalTableModel, QSqlQuery, Model/View Programming, and Query Model Example.

Member Function Documentation

 while (myModel->canFetchMore())
     myModel->fetchMore();

 QVariant MyModel::data(const QModelIndex &item, int role) const
 {
     if (item.column() == m_specialColumnNo) {
         // handle column separately
     }
     return QSqlQueryModel::data(item, role);
 }

 QSqlQueryModel model;
 model.setQuery("select * from MyTable");
 if (model.lastError().isValid())
     qDebug() << model.lastError();