Calculated amount in Interface aren't not saved into SQLlite DB, only different amount is being saved

Question

I'm having problem with the calculations. When build the system and test it, the correct amount showed in the interface isn't showing up/saved in database. The amount is something different than the one in the interface.

Note:

1. SELECT SUM(TotalPrice) FROM Sold (Screenshot of the Sold table will be attached together.
2. I will attach the screenshots below. Have a look on it to get clear picture of the situation.
3. I've marked the problem code with the comment //<--THIS-->//.

Here's my code:

void CashRegister::on_pushButton_next_clicked()
{
    ui->tableView->show();
    ui->pushButton_finish->show();
    ui->label_totalAmount->show();

    QString receiptNo = ui->label_receiptNum->text();
    QString itemSelect = ui->comboBox_itemID->currentText();
    QString qtySold = ui->lineEdit_qtySold->text();
    QDate currentDate = QDate::currentDate();   //<--Solved-->//
    //QString totalPrice1 = ui->label_totalAmount->text();

    double price=0, totalPrice=0;

    QSqlQuery myqry;
    myqry.exec("SELECT ItemPrice, ItemName FROM Item WHERE ItemId='"+itemSelect+"' ");
    if (myqry.next())
        price = myqry.value(0).toDouble();

    totalPrice = price * qtySold.toInt();

    QString totalPriceString = QString::number(totalPrice);

    myqry.prepare("INSERT INTO Sold (ReceiptId, ItemId, SoldQuantity, TotalPrice) VALUES ('"+receiptNo+"', '"+itemSelect+"', '"+qtySold+"', '"+totalPriceString+"') ");
    myqry.exec();

    ui->comboBox_itemID->setCurrentIndex(0);
    ui->lineEdit_qtySold->clear();

    myqry.prepare("SELECT Item.ItemId, Item.ItemName, Item.ItemPrice, Sold.SoldQuantity FROM Item, Sold WHERE Item.ItemId = Sold.ItemId AND Sold.ReceiptId='"+receiptNo+"' ");
    myqry.exec();


    QSqlQueryModel *myModel = new QSqlQueryModel();
    myModel->setQuery(myqry);
    ui->tableView->setModel(myModel);

    double sum = 0;

    myqry.exec("SELECT SUM(TotalPrice) FROM Sold WHERE ReceiptId = '"+receiptNo+"' ");
    if (myqry.next())
        sum += myqry.value(0).toDouble();

    ui->label_totalAmount->setText("TOTAL AMOUNT: RM" + QString::number(sum));

    QString totalPriceReceipt = QString::number(sum);

    //<--THIS-->//
    myqry.prepare("INSERT INTO Receipt (ReceiptId, ReceiptDate, ReceiptAmount) VALUES ('"+receiptNo+"', '"+currentDate.toString()+"', '"+totalPriceReceipt+"') ");
    myqry.exec();
}