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<h1 class="title">Presenting Data in a Table View<br /><span class="subtitle"></span>
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<p>The <a href="qsqlquerymodel.html">QSqlQueryModel</a>, <a href="qsqltablemodel.html">QSqlTableModel</a>, and <a href="qsqlrelationaltablemodel.html">QSqlRelationalTableModel</a> classes can be used as a data source for Qt's view classes such as <a href="qlistview.html">QListView</a>, <a href="qtableview.html">QTableView</a>, and <a href="qtreeview.html">QTreeView</a>. In practice, <a href="qtableview.html">QTableView</a> is by far the most common choice, because an SQL result set is essentially a two-dimensional data structure.</p>
<p align="center"><img src="images/relationaltable.png" alt="A table view displaying a QSqlTableModel" /></p><p>The following example creates a view based on an SQL data model:</p>
<pre> QTableView *view = new QTableView;
view->setModel(model);
view->show();</pre>
<p>If the model is a read-write model (e.g., <a href="qsqltablemodel.html">QSqlTableModel</a>), the view lets the user edit the fields. You can disable this by calling</p>
<pre> view->setEditTriggers(QAbstractItemView::NoEditTriggers);</pre>
<p>You can use the same model as a data source for multiple views. If the user edits the model through one of the views, the other views will reflect the changes immediately. The <a href="sql-tablemodel.html">Table Model</a> example shows how it works.</p>
<p>View classes display a header at the top to label the columns. To change the header texts, call <a href="qabstractitemmodel.html#setHeaderData">setHeaderData()</a> on the model. The header's labels default to the table's field names. For example:</p>
<pre> model->setHeaderData(0, Qt::Horizontal, QObject::tr("ID"));
model->setHeaderData(1, Qt::Horizontal, QObject::tr("Name"));
model->setHeaderData(2, Qt::Horizontal, QObject::tr("City"));
model->setHeaderData(3, Qt::Horizontal, QObject::tr("Country"));</pre>
<p><a href="qtableview.html">QTableView</a> also has a vertical header on the left with numbers identifying the rows. If you insert rows programmatically using <a href="qsqltablemodel.html#insertRows">QSqlTableModel::insertRows</a>(), the new rows will be marked with an asterisk (*) until they are submitted using <a href="qsqltablemodel.html#submitAll">submitAll()</a> or automatically when the user moves to another record (assuming the <a href="qsqltablemodel.html#EditStrategy-enum">edit strategy</a> is <a href="qsqltablemodel.html#EditStrategy-enum">QSqlTableModel::OnRowChange</a>).</p>
<p align="center"><img src="images/insertrowinmodelview.png" alt="Inserting a row in a model" /></p><p>Likewise, if you remove rows using <a href="qsqltablemodel.html#removeRows">removeRows()</a>, the rows will be marked with an exclamation mark (!) until the change is submitted.</p>
<p>The items in the view are rendered using a delegate. The default delegate, <a href="qitemdelegate.html">QItemDelegate</a>, handles the most common data types (<tt>int</tt>, <a href="qstring.html">QString</a>, <a href="qimage.html">QImage</a>, etc.). The delegate is also responsible for providing editor widgets (e.g., a combobox) when the user starts editing an item in the view. You can create your own delegates by subclassing <a href="qabstractitemdelegate.html">QAbstractItemDelegate</a> or <a href="qitemdelegate.html">QItemDelegate</a>. See <a href="model-view-programming.html">Model/View Programming</a> for more information.</p>
<p><a href="qsqltablemodel.html">QSqlTableModel</a> is optimized to operate on a single table at a time. If you need a read-write model that operates on an arbitrary result set, you can subclass <a href="qsqlquerymodel.html">QSqlQueryModel</a> and reimplement <a href="qabstractitemmodel.html#flags">flags()</a> and <a href="qabstractitemmodel.html#setData">setData()</a> to make it read-write. The following two functions make fields 1 and 2 of a query model editable:</p>
<pre> Qt::ItemFlags EditableSqlModel::flags(
const QModelIndex &index) const
{
Qt::ItemFlags flags = QSqlQueryModel::flags(index);
if (index.column() == 1 || index.column() == 2)
flags |= Qt::ItemIsEditable;
return flags;
}
bool EditableSqlModel::setData(const QModelIndex &index, const QVariant &value, int <span class="comment">/* role */</span>)
{
if (index.column() < 1 || index.column() > 2)
return false;
QModelIndex primaryKeyIndex = QSqlQueryModel::index(index.row(), 0);
int id = data(primaryKeyIndex).toInt();
clear();
bool ok;
if (index.column() == 1) {
ok = setFirstName(id, value.toString());
} else {
ok = setLastName(id, value.toString());
}
refresh();
return ok;
}</pre>
<p>The setFirstName() helper function is defined as follows:</p>
<pre> bool EditableSqlModel::setFirstName(int personId, const QString &firstName)
{
QSqlQuery query;
query.prepare("update person set firstname = ? where id = ?");
query.addBindValue(firstName);
query.addBindValue(personId);
return query.exec();
}</pre>
<p>The setLastName() function is similar. See the <a href="sql-querymodel.html">Query Model</a> example for the complete source code.</p>
<p>Subclassing a model makes it possible to customize it in many ways: You can provide tooltips for the items, change the background color, provide calculated values, provide different values for viewing and editing, handle null values specially, and more. See <a href="model-view-programming.html">Model/View Programming</a> as well as the <a href="qabstractitemview.html">QAbstractItemView</a> reference documentation for details.</p>
<p>If all you need is to resolve a foreign key to a more human-friendly string, you can use <a href="qsqlrelationaltablemodel.html">QSqlRelationalTableModel</a>. For best results, you should also use <a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate</a>, a delegate that provides combobox editors for editing foreign keys.</p>
<p align="center"><img src="images/relationaltable.png" alt="Editing a foreign key in a relational table" /></p><p>The <a href="sql-relationaltablemodel.html">Relational Table Model</a> example illustrates how to use <a href="qsqlrelationaltablemodel.html">QSqlRelationalTableModel</a> in conjunction with <a href="qsqlrelationaldelegate.html">QSqlRelationalDelegate</a> to provide tables with foreign key support.</p>
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