From C++ (Qt):

Qt Code: 
  1. int main(int argc, char *argv[])
  2. {
  3.     QApplication app(argc, argv);
  4.  
  5.     /*
  6.      * I have omitted the code about connection with the database and all for ease of   
  7.      * viewing the code.
  8.      */
  9.  
  10.  
  11.     // My own function for filling in the data in the `QSqlQueryModel`
  13.     QString binid = "B1";
  14.     QString query = "SELECT t1.BinId, t1.PartitionId, t2.UnitId, t2.ItemCount FROM Bin_Partitions AS t1 "
  15.                     "INNER JOIN Partition_Units AS t2 ON t1.PartitionId = t2.PartitionId "
  16.                     "WHERE t1.BinId ='" + binid + "'";
  17.     model->setQuery(query);
  18.  
  19.     /*
  20.      * I can see that the query runs successfully because the following
  21.      * QTableView DOES get populated properly. 
  22.      */
  23.     // Use QTableView to visualize
  24.     QTableView *view = new QTableView;
  25.     view->setModel(model);
  26.     view->show();
  27.  
  28.     QQmlApplicationEngine engine;
  29.     // Passing the same model to QML for displaying in the TableView.
  30.     engine.rootContext()->setContextProperty ("SQQL", model);
  31.     engine.load(QUrl(QStringLiteral("/home/.../main.qml")));
  32.  
  33.     QObject               *topLevel  = engine.rootObjects ().value (0);
  34.     QQuickWindow          *window    = qobject_cast <QQuickWindow *> (topLevel);
  35.  
  36.     return app.exec();
  37. }
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From QML:
Qt Code: 
  1. import QtQuick 2.2
  2. import QtQuick.Window 2.1
  3. import QtQuick.Controls 1.2
  4.  
  5. Window
  6. {
  7.     visible: true
  8.     width: 360
  9.     height: 360
  10.     color: "blue"
  11.  
  12.     TableView
  13.     {
  14.         TableViewColumn{ role: "col1" ; title: "BinId" ; visible: true}
  15.         TableViewColumn{ role: "col2" ; title: "PartitionId" }
  16.         TableViewColumn{ role: "col3" ; title: "UnitId" }
  17.         TableViewColumn{ role: "col4" ; title: "ItemCount" }
  18.  
  19.         model: SQQL
  20.     }
  21. }
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The TableView of QML shows up EMPTY!

I need help.