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<td align="right" valign="top" width="230"><a href="http://www.trolltech.com"><img src="images/trolltech-logo.png" align="right" width="203" height="32" border="0" /></a></td></tr></table><h1 align="center">QSqlRelationalTableModel Class Reference<br /><sup><sup>[<a href="qtsql.html">QtSql</a> module]</sup></sup></h1>
<p>The QSqlRelationalTableModel class provides an editable data model for a single database table, with foreign key support. <a href="#details">More...</a></p>
<pre> #include <QSqlRelationalTableModel></pre><p>Inherits <a href="qsqltablemodel.html">QSqlTableModel</a>.</p>
<ul>
<li><a href="qsqlrelationaltablemodel-members.html">List of all members, including inherited members</a></li>
</ul>
<a name="public-functions"></a>
<h3>Public Functions</h3>
<ul>
<li><div class="fn"/><b><a href="qsqlrelationaltablemodel.html#QSqlRelationalTableModel">QSqlRelationalTableModel</a></b> ( QObject * <i>parent</i> = 0, QSqlDatabase <i>db</i> = QSqlDatabase() )</li>
<li><div class="fn"/>virtual <b><a href="qsqlrelationaltablemodel.html#dtor.QSqlRelationalTableModel">~QSqlRelationalTableModel</a></b> ()</li>
<li><div class="fn"/>QSqlRelation <b><a href="qsqlrelationaltablemodel.html#relation">relation</a></b> ( int <i>column</i> ) const</li>
<li><div class="fn"/>virtual QSqlTableModel * <b><a href="qsqlrelationaltablemodel.html#relationModel">relationModel</a></b> ( int <i>column</i> ) const</li>
<li><div class="fn"/>virtual bool <b><a href="qsqlrelationaltablemodel.html#setData">setData</a></b> ( const QModelIndex & <i>index</i>, const QVariant & <i>value</i>, int <i>role</i> = Qt::EditRole )</li>
<li><div class="fn"/>virtual void <b><a href="qsqlrelationaltablemodel.html#setRelation">setRelation</a></b> ( int <i>column</i>, const QSqlRelation & <i>relation</i> )</li>
</ul>
<ul>
<li><div class="fn"/>20 public functions inherited from <a href="qsqltablemodel.html#public-functions">QSqlTableModel</a></li>
<li><div class="fn"/>15 public functions inherited from <a href="qsqlquerymodel.html#public-functions">QSqlQueryModel</a></li>
<li><div class="fn"/>1 public function inherited from <a href="qabstracttablemodel.html#public-functions">QAbstractTableModel</a></li>
<li><div class="fn"/>34 public functions inherited from <a href="qabstractitemmodel.html#public-functions">QAbstractItemModel</a></li>
<li><div class="fn"/>29 public functions inherited from <a href="qobject.html#public-functions">QObject</a></li>
</ul>
<h3>Additional Inherited Members</h3>
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<li><div class="fn"/>1 property inherited from <a href="qobject.html#properties">QObject</a></li>
<li><div class="fn"/>4 public slots inherited from <a href="qsqltablemodel.html#public-slots">QSqlTableModel</a></li>
<li><div class="fn"/>2 public slots inherited from <a href="qabstractitemmodel.html#public-slots">QAbstractItemModel</a></li>
<li><div class="fn"/>1 public slot inherited from <a href="qobject.html#public-slots">QObject</a></li>
<li><div class="fn"/>4 signals inherited from <a href="qsqltablemodel.html#signals">QSqlTableModel</a></li>
<li><div class="fn"/>14 signals inherited from <a href="qabstractitemmodel.html#signals">QAbstractItemModel</a></li>
<li><div class="fn"/>1 signal inherited from <a href="qobject.html#signals">QObject</a></li>
<li><div class="fn"/>5 static public members inherited from <a href="qobject.html#static-public-members">QObject</a></li>
<li><div class="fn"/>8 protected functions inherited from <a href="qsqltablemodel.html#protected-functions">QSqlTableModel</a></li>
<li><div class="fn"/>3 protected functions inherited from <a href="qsqlquerymodel.html#protected-functions">QSqlQueryModel</a></li>
<li><div class="fn"/>14 protected functions inherited from <a href="qabstractitemmodel.html#protected-functions">QAbstractItemModel</a></li>
<li><div class="fn"/>7 protected functions inherited from <a href="qobject.html#protected-functions">QObject</a></li>
</ul>
<a name="details"></a>
<hr />
<h2>Detailed Description</h2>
<p>The QSqlRelationalTableModel class provides an editable data model for a single database table, with foreign key support.</p>
<p>QSqlRelationalTableModel acts like <a href="qsqltablemodel.html">QSqlTableModel</a>, but allows columns to be set as foreign keys into other database tables.</p>
<p><table align="center" cellpadding="2" cellspacing="1" border="0">
<tr valign="top" class="odd"><td><img src="images/noforeignkeys.png" /></td><td><img src="images/foreignkeys.png" /></td></tr>
</table></p>
<p>The screenshot on the left shows a plain <a href="qsqltablemodel.html">QSqlTableModel</a> in a <a href="qtableview.html">QTableView</a>. Foreign keys (<tt>city</tt> and <tt>country</tt>) aren't resolved to human-readable values. The screenshot on the right shows a QSqlRelationalTableModel, with foreign keys resolved into human-readable text strings.</p>
<p>The following code snippet shows how the QSqlRelationalTableModel was set up:</p>
<pre> model->setTable("employee");
model->setRelation(2, QSqlRelation("city", "id", "name"));
model->setRelation(3, QSqlRelation("country", "id", "name"));</pre>
<p>The <a href="qsqlrelationaltablemodel.html#setRelation">setRelation</a>() function calls establish a relationship between two tables. The first call specifies that column 2 in table <tt>employee</tt> is a foreign key that maps with field <tt>id</tt> of table <tt>city</tt>, and that the view should present the <tt>city</tt>'s <tt>name</tt> field to the user. The second call does something similar with column 3.</p>
<p>If you use a read-write QSqlRelationalTableModel, you probably want to use <a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate</a> on the view. Unlike the default delegate, <a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate</a> provides a combobox for fields that are foreign keys into other tables. To use the class, simply call <a href="qabstractitemview.html#setItemDelegate">QAbstractItemView::setItemDelegate</a>() on the view with an instance of <a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate</a>:</p>
<pre> QTableView *view = new QTableView;
view->setModel(model);
view->setItemDelegate(new QSqlRelationalDelegate(view));</pre>
<p>The <a href="sql-relationaltablemodel.html">sql/relationaltablemodel</a> example illustrates how to use QSqlRelationalTableModel in conjunction with <a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate</a> to provide tables with foreigh key support.</p>
<p align="center"><img src="images/relationaltable.png" /></p><p>Notes:</p>
<ul>
<li>The table's primary key may not contain a relation to another table.</li>
<li>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.</li>
</ul>
<p>See also <a href="qsqlrelation.html">QSqlRelation</a>, <a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate</a>, and <a href="sql-relationaltablemodel.html">Relational Table Model Example</a>.</p>
<hr />
<h2>Member Function Documentation</h2>
<h3 class="fn"><a name="QSqlRelationalTableModel"></a>QSqlRelationalTableModel::QSqlRelationalTableModel ( <a href="qobject.html">QObject</a> * <i>parent</i> = 0, <a href="qsqldatabase.html">QSqlDatabase</a> <i>db</i> = QSqlDatabase() )</h3>
<p>Creates an empty <a href="qsqlrelationaltablemodel.html">QSqlRelationalTableModel</a> and sets the parent to <i>parent</i> and the database connection to <i>db</i>. If <i>db</i> is not valid, the default database connection will be used.</p>
<h3 class="fn"><a name="dtor.QSqlRelationalTableModel"></a>QSqlRelationalTableModel::~QSqlRelationalTableModel () <tt> [virtual]</tt></h3>
<p>Destroys the object and frees any allocated resources.</p>
<h3 class="fn"><a name="relation"></a><a href="qsqlrelation.html">QSqlRelation</a> QSqlRelationalTableModel::relation ( int <i>column</i> ) const</h3>
<p>Returns the relation for the column <i>column</i>, or an invalid relation if no relation is set.</p>
<p>See also <a href="qsqlrelationaltablemodel.html#setRelation">setRelation</a>() and <a href="qsqlrelation.html#isValid">QSqlRelation::isValid</a>().</p>
<h3 class="fn"><a name="relationModel"></a><a href="qsqltablemodel.html">QSqlTableModel</a> * QSqlRelationalTableModel::relationModel ( int <i>column</i> ) const <tt> [virtual]</tt></h3>
<p>Returns a <a href="qsqltablemodel.html">QSqlTableModel</a> object for accessing the table for which <i>column</i> is a foreign key, or 0 if there is no relation for the given <i>column</i>.</p>
<p>The returned object is owned by the <a href="qsqlrelationaltablemodel.html">QSqlRelationalTableModel</a>.</p>
<p>See also <a href="qsqlrelationaltablemodel.html#setRelation">setRelation</a>() and <a href="qsqlrelationaltablemodel.html#relation">relation</a>().</p>
<h3 class="fn"><a name="setData"></a>bool QSqlRelationalTableModel::setData ( const <a href="qmodelindex.html">QModelIndex</a> & <i>index</i>, const <a href="qvariant.html">QVariant</a> & <i>value</i>, int <i>role</i> = Qt::EditRole ) <tt> [virtual]</tt></h3>
<p>Sets the data for the <i>role</i> in the item with the specified <i>index</i> to the <i>value</i> given. Depending on the edit strategy, the value might be applied to the database at once, or it may be cached in the model.</p>
<p>Returns true if the value could be set, or false on error (for example, if <i>index</i> is out of bounds).</p>
<p>For relational columns, <i>value</i> must be the index, not the display value.</p>
<p>Reimplemented from <a href="qabstractitemmodel.html#setData">QAbstractItemModel</a>.</p>
<p>See also <a href="qsqltablemodel.html#editStrategy">editStrategy</a>(), <a href="qabstractitemmodel.html#data">data</a>(), <a href="qsqltablemodel.html#submit">submit</a>(), and <a href="qsqltablemodel.html#revertRow">revertRow</a>().</p>
<h3 class="fn"><a name="setRelation"></a>void QSqlRelationalTableModel::setRelation ( int <i>column</i>, const <a href="qsqlrelation.html">QSqlRelation</a> & <i>relation</i> ) <tt> [virtual]</tt></h3>
<p>Lets the specified <i>column</i> be a foreign index specified by <i>relation</i>.</p>
<p>Example:</p>
<pre> model->setTable("employee");
model->setRelation(2, QSqlRelation("city", "id", "name"));</pre>
<p>The setRelation() call specifies that column 2 in table <tt>employee</tt> is a foreign key that maps with field <tt>id</tt> of table <tt>city</tt>, and that the view should present the <tt>city</tt>'s <tt>name</tt> field to the user.</p>
<p>Note: The table's primary key may not contain a relation to another table.</p>
<p>See also <a href="qsqlrelationaltablemodel.html#relation">relation</a>().</p>
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