Select data from database SQLite error - Help please!

[sousadaniel7]

Good afternoon.

How do I do a SELECT to an SQLite database?

I have the following:

QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
 
    db.setDatabaseName("bd_agt");
 
    if(db.open()){
        qDebug() << "Opening database, status: " << db.open();
    }
 
    QSqlQuery query("SELECT * FROM tag");
         while (query.next()) {
             QString nome = query.value(1).toString();
             ui->label->setText(nome);
         }
 
         qDebug() << query.size();

QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");

    db.setDatabaseName("bd_agt");

    if(db.open()){
        qDebug() << "Opening database, status: " << db.open();
    }

    QSqlQuery query("SELECT * FROM tag");
         while (query.next()) {
             QString nome = query.value(1).toString();
             ui->label->setText(nome);
         }

         qDebug() << query.size();

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But in query.size () always returns -1, but I have values ​​in the database
How can I fix this?

Regards,
Daniel Sousa