QSqlQuery error

[gabor53]

Hi,
I've spent quite some time trying to figure out what's wrong with this code. Whenever I run it I get the following messages:
The database is open!
QSqlQuery::value: not positioned on a valid record

The code:

    QSqlDatabase db;
    db = QSqlDatabase::addDatabase ("QSQLITE");
    db.setDatabaseName ("C:/Programming/Qtsamples/Image_from_DB/db.db");
	db.open ();

    QSqlQuery query;

    if(!db.open ())
    {
        qDebug() << "The database is NOT open!";
    }
    else
    {
        qDebug() << "The database is open!";
    }

    query.prepare ("SELECT Pic FROM Items");
    query.exec ();



    query.first ();
	QByteArray ByteArray;
	ByteArray = query.value (1).toByteArray ();
    QPixmap Pixmap = QPixmap();
    Pixmap.loadFromData (ByteArray);
    db.close ();

	ui->label->setPixmap (Pixmap);
    ui->label->show ();

Please help me to make it positioned on a valid record!
Thank you.

[kshegunov]

@gabor53
Hello,
You select one column from the table, but try to retrieve the second column from the resultset, try:

    query.value(0).toByteArray();

Additional (potential) problems exist in your code:

• In example, you don't handle the return value of your QSqlDatabase::first call, it's supposed to tell you whether you're properly positioned at the first record or not.
• You call QSqlDatabase::open twice, you can use QSqlDatabase::isOpen to check if your database was properly opened instead of trying to open it again.
• You don't handle the return value of QSqlQuery::exec as well.
• There is no need to really prepare the query before execution, you don't intend to use it multiple times with different bindings.
• You close your database after executing the query. Usually the idea is to open/close the database once and have multiple queries executed on the same database instance.

Kind regards.

[gabor53]

Thank you. it worked.