calculated columns for QSqlRelationalTableModel

I'm working on an app for a MySQL db. One of the tables features 3 columns that I'd like to sum up per row and then a subtotal for all rows for those 3 columns.
I managed to get the column subtotals, but for the row total (for the 3 fields of that particular row), I would need a calculated field.

After googling, the only reference I could find is this thread:
http://lists.trolltech.com/qt-intere...ad00142-0.html

would that be the best way to approach this or is it possible to change the underlying SQL for the QSqlRelationalTableModel?

cheers,
-A

I tried what was suggested in the link, but it doesn't work, i.e. the newly calculated row doesn't show, even though I inserted the new column in my instance of my custom model (based on QSqlRelationalTableModel).

my data method looks like this:

Code:

---

QVariant CustomModel::data(const QModelIndex &index, int role) const
{
    QVariant value = QSqlRelationalTableModel::data(index,role);
 
    if(role == Qt::TextAlignmentRole && (index.column() == 4 || index.column() ==5 || index.column() == 6))
        value = QVariant(Qt::AlignRight | Qt::AlignVCenter);
    else if(role == Qt::DisplayRole && index.column() == 7)
    {
        QModelIndex mi = this->index(index.row(),4,QModelIndex());
 
        value = QVariant(mi.data(role)) ;
    }
    else
        value = QSqlRelationalTableModel::data(index, role);
 
    return value;
}

---

what am I missing?