how execut a query of sqlite in QT

i have ubutnu 14.04 i'm working with Qt , i have a database ( sqlite ) , i will to get the information with my data base what is the problem ? my code : SELECT * FROM expert

database = QSqlDatabase::addDatabase("QSQLITE");
 database.setDatabaseName(nameofdatabase);

 if (!database.open())
 {
    qDebug() << "Error: connection with database fail";
 }
 else
 {
    qDebug() << "Database: connection ok";
 }



 QSqlQuery query;
 QString queryString = "SELECT * FROM expert";
 query.exec("SELECT * FROM expert");

 if(query.exec())
 {
     qDebug() << "true";
 }
 else
 {
      qDebug() << "erre";
 }

if ( ! query.next() ) {
QSqlRecord record = query.record();
QString x = "Expert_id";
qDebug() <<  record.value(1);
}

the result :

Database: connection ok 
erre 
QVariant(Invalid) 

what is the problem ?