Problem of closing database

[cooper]

Thanks ChrisW67.

Can i have another question please?
as you see in my code:

QSqlQuery query;
        query.exec("PRAGMA synchronous = OFF");
        model = new QSqlTableModel(this);
        model->setEditStrategy(QSqlTableModel::OnManualSubmit);
 
        model->setTable("c1");
        model->select();
        model->insertRow(0);
        model->setData(model->index(0, 1), String(qdatetime.toString(Qt::ISODate)));
        model->setData(model->index(0, 2), String(qdatetime.toString(Qt::ISODate)));
        model->setData(model->index(0, 3), 1);  // original value is 1 in int 
        model->submitAll();

QSqlQuery query;
        query.exec("PRAGMA synchronous = OFF");
        model = new QSqlTableModel(this);
        model->setEditStrategy(QSqlTableModel::OnManualSubmit);
        
        model->setTable("c1");
        model->select();
        model->insertRow(0);
        model->setData(model->index(0, 1), String(qdatetime.toString(Qt::ISODate)));
        model->setData(model->index(0, 2), String(qdatetime.toString(Qt::ISODate)));
        model->setData(model->index(0, 3), 1);  // original value is 1 in int 
        model->submitAll();

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when i click 'stop' button, i want to change the value in last row. here is my code:

model->setTable("c1");
        model->select();
        int row = model->rowCount();
        model->setData(model->index(row, 3), 55); // change the value to be 55 in int
        model->sumitAll();

model->setTable("c1");
        model->select();
        int row = model->rowCount();
        model->setData(model->index(row, 3), 55); // change the value to be 55 in int
        model->sumitAll();

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however, after i stop my program and take a look database, the last value in (row, 3) has not been changed.

can you point out where i did wrong please?
I really appreciate your help.