QSQLITE database can't exec queries

[mcwar]

Why this code is not working?

db = QSqlDatabase::addDatabase("QSQLITE"); //I defined the "db" at header.
    db.setDatabaseName("../database");
    db.open();
    QSqlQuery query(db);
    query.exec("SELECT id FROM lesson");
    QMessageBox::about(0,"",query.value(0).toString());

db = QSqlDatabase::addDatabase("QSQLITE"); //I defined the "db" at header.
    db.setDatabaseName("../database");
    db.open();
    QSqlQuery query(db);
    query.exec("SELECT id FROM lesson");
    QMessageBox::about(0,"",query.value(0).toString());

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code is running without any error but value which in message box is null. There is no result at query value.

[wysota]

Probably your relative path to the database is incorrect. See if QFile::exists("../database") returns true (check that before you open the database) and if that's indeed the database file you want.

[mcwar]

I checked that. I am not a newbie. db.open returned true, db.exists returned true also db.tables return my tables but it can't exec queries.

[wysota]

Ah, now I see the problem. You forgot to position the cursor on the first row of the result. Run query.first() before calling query.value().

BTW. db.open() and db.exist() will always return true in case of SQLite (provided you have sufficient access rights to access the database file) so that's not a proof of anything.

[mcwar]

Oh thanks, it is running.

[tangential]

Of note, query.next() also functions as query.first() if it's the first navigation call in the program flow.