source: trunk/doc/src/porting/qt4-sql.qdoc@ 561

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/*!
    \page qt4-sql.html
    \title The Qt 4 Database GUI Layer

    \contentspage {What's New in Qt 4}{Home}
    \previouspage Cross-Platform Accessibility Support in Qt 4
    \nextpage The Network Module in Qt 4

    The GUI layer of the SQL module in Qt 4 has been entirely
    redesigned to work with \l{qt4-interview.html}{Interview} (Qt's
    new model/view classes). It consists of three model classes
    (QSqlQueryModel, QSqlTableModel, and QSqlRelationalTableModel)
    that can be used with Qt's view classes, notably QTableView.

    \section1 General Overview

    The Qt 4 SQL classes are divided into three layers:

    \list
    \o The database drivers
    \o The core SQL classes
    \o The GUI classes
    \endlist

    The database drivers and the core SQL classes are mostly the same
    as in Qt 3. The database item models are new with Qt 4; they
    inherit from QAbstractItemModel and make it easy to present data
    from a database in a view class such as QListView, QTableView,
    and QTreeView.

    The philosophy behind the Qt 4 SQL module is that it should be
    possible to use database models for rendering and editing data
    just like any other item models. By changing the model at
    run-time, you can decide whether you want to store your data in
    an SQL database or in, say, an XML file. This generic approach
    has the additional benefit that you don't need to know anything
    about SQL to display and edit data.

    The Qt 4 SQL module includes three item models:

    \list
    \o QSqlQueryModel is a read-only model based on an arbitrary
       SQL query.
    \o QSqlTableModel is a read-write model that works on a single
       table.
    \o QSqlRelationalTableModel is a QSqlTableModel subclass with
       foreign key support.
    \endlist

    Combined with Qt's view classes and Qt's default delegate class
    (QItemDelegate), the models offer a very powerful mechanism for
    accessing databases. For finer control on the rendering of the
    fields, you can subclass one of the predefined models, or even
    QAbstractItemDelegate or QItemDelegate if you need finer control.

    You can also perform some customizations without subclassing. For