title: QSqlQuery Insert into database doesn't work
body: <p>I use <code>PyQt4.QtSql.QSqlQuery</code>. I get values from a Form and want to Insert them into the database. I open a connection and try to Add, but there are no values in the database and no errors. What's the problem?</p>
  
  <pre><code>    db      = QSqlDatabase.addDatabase("QMYSQL")
  
      db.setHostName("localhost")
      db.setDatabaseName("vista")
      db.setUserName("root")
      db.setPassword("secret")
  
      if (db.open()==False):     
          QMessageBox.critical(None, "Database Error",
              db.lastError().text())   
      query = QSqlQuery()
      query.prepare("INSERT INTO user (fio, sex,polis,document,birtday) "
        "VALUES (:fio, :sex,:polis,:document,:birtday)");
      query.bindValue(":fio", fio);
      query.bindValue(":sex", sex);
      query.bindValue(":polis", polis);
      query.bindValue(":document", document);
      query.bindValue(":birtday", birtday);
      query.exec_();
  </code></pre>