QSqlQuery with MySQL performs twicely (SOLVED)

Hi, I will be very glad to get a quick answer. I'm using QSqlQuery with QSqlDatabase with MySQL. I try to exec one query but client shows two entries in the table. Why?

Code:

#include <QtGui/QApplication>
#include "MainWindow.h"
 
#include <QMetaType>
#include <QTextCodec>
 
#include <QSqlDatabase>
#include <QSqlQuery>
 
int main(int argc, char *argv[])
{
    QApplication app(argc, argv);
 
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setUserName("root");
    db.setPassword("password0");
    db.setDatabaseName("fitnesscenter");
    db.open();
 
    QSqlQuery query("insert into users(fullname) values ('Someone')");
    query.exec();
}

Code:

mysql> delete from users;
Query OK, 2 rows affected (0.04 sec)
 
mysql> select * from users;
+----+----------+----------+
| id | fullname | password |
+----+----------+----------+
| 39 | Someone  | NULL     |
| 40 | Someone  | NULL     |
+----+----------+----------+
2 rows in set (0.00 sec)
 
mysql>

EDIT:

This post contains the right answer:
http://www.qtcentre.org/threads/4550...742#post206742
It is extremely unobvious!