Submitting QSqlRecord to MySQL database

I want to access a MySQL database and I want to read+write data from+to the database within my Qt/C++ program. For the read write process, I try to use QSqlTableModel, QSqlTableRcord and QSqlDatabase as this is a very pleasant approach without too much of SQL commands which I dislike for the one or other reason (to handle myself). I got a similar approach already running (so the database is running already) but it is cluttered all over. So the simple question is what am I doing wrong within these few lines of example code: Using QT 4.5.x The test database has 3 columns: float x, float y, blob img

Code:

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int main(){
QImage img("./some_image.png");
QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setHostName("localhost");
db.setDatabaseName("test");
db.setPort(3306);
db.setUserName("root");
db.setPassword("xxxxxxx");
if (!db.open() )
    qDebug("Mising db / unable to open");
else {
    QSqlTableModel model;
    qDebug() << "tables::" <<db.tables(); //so I see the table exists and gets detected
    model.setTable("test_table");
 
    QSqlRecord rec;
    rec.setValue(0,1.0f);
    rec.setValue(1,2.0f);
 
    QByteArray ba;
    QBuffer buffer(&ba);
    buffer.open(QIODevice::WriteOnly);
    img.save(&buffer, "PNG");
    rec.setValue(2,ba);
 
    model.insertRecord(0,rec);
    if (model.lastError().isVaild())
        qDebug() << model.lastError().text();
    if (!model.submitAll())
        qDebug() << "Submit all did not work";
    return 0;
    }

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Thx for any help, I already run from one end of the Qt docs to the other but did not find a solution and I already wasted 5 hours doing that, so I am thankful for any hint (unless you suggest to do it completely different).

Maybe I have a wrong picture of QSqlRecord in my head, plx tell me if so.

Anyone? I really would like to know.