error with QSqlQuery

[mmm286]

Hi,

I'm trying to do a select of a database like this:

db.setHostName("xx.xx.xx.xx");
 
    db.setDatabaseName("prueba");
    db.setUserName("xxxxxxx");
    db.setPassword("yyyyyy");
 
    if (!db.open())
    {
        QMessageBox::information(this, "Application name","not connected");
        QMessageBox::information(this,"",db.lastError().text());
    }
 
    QSqlQuery query;
 
   // bool r=db.open();
    if( db.open() ) {
                    query = QSqlQuery("select * from USERSGROUPS");
                    //query.exec();
                    bool prueba = query.exec();
                    qDebug() << query.lastError().text();
                    QMessageBox::information(this,"",query.lastError().text());

db.setHostName("xx.xx.xx.xx");
   
    db.setDatabaseName("prueba");
    db.setUserName("xxxxxxx");
    db.setPassword("yyyyyy");

    if (!db.open())
    {
        QMessageBox::information(this, "Application name","not connected");
        QMessageBox::information(this,"",db.lastError().text());
    }

    QSqlQuery query;

   // bool r=db.open();
    if( db.open() ) {
                    query = QSqlQuery("select * from USERSGROUPS");
                    //query.exec();
                    bool prueba = query.exec();
                    qDebug() << query.lastError().text();
                    QMessageBox::information(this,"",query.lastError().text());

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it gives me: [Microsoft][ODBC controllers admin] Function sequence error QODBC3: Unable to execute statement

Could you help me please?
Many thanks and sorry for my english!