QT can't operate QSqlite

#include <QApplication>
#include <iostream>
#include <QSqlDatabase>
#include <QSqlQuery>
#include <QSqlDriver>
#include <QStringList>
#include <QtGui>
using namespace std;

int main(int argc, char *argv[])
{
    QTextCodec::setCodecForTr(QTextCodec::codecForName("gbk"));
    QApplication a(argc,argv);

    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
   db.setDatabaseName("Test.db3");
   bool ok = db.open();
   QSqlQuery query;
   if(ok)
  {
     qDebug()<< query.exec("insert into t_user values('xive','activ')");
  }

  return a.exec();
}

Above all is my code,my QT version is 4.6.3,sqlite version is 3.6.23.1. I create a table in sqlite.I can open the db.but i can't do anything,such as insert ,select ... so i need you help.thank you