Qt Checking Login using Database - mysql

Question

I am using qt to create a user login. I am using Sqlite as my database and am stuck for some reason it is not working properly. I was able to corectly bypass the login screen only when typing in the first row from the database. Any other user cannot log in (row 2, 3,4 ... in database). I have been reading all kinds of posts for the past days and have not come to a proper solution. Here is my code. I have also tried creating a query through QSqlQuery and passing it into the QSQlQueryModel Object which did not work at all.
void MainWindow::on_login_clicked()
{
QSqlDatabase m_db;
QString path = "C:/Users/annea/Summer2019Database.db";
m_db = QSqlDatabase::addDatabase("QSQLITE");
m_db.setDatabaseName(path);
m_db.open();
if (!m_db.open())
{
qDebug() << "Error: connection with database fail";
}
else
{
qDebug() << "Database: connection ok";
}
QString username = ui->username->text();
QString password = ui->password->text();
QSqlQueryModel *queryModel = new QSqlQueryModel;
queryModel->setQuery("SELECT * FROM [User Database] WHERE Username= username"); //select the row of where the Username == username
queryModel->query().exec(); //execute it (not really sure why or what this does
if(queryModel->record(0).value(1).toString()== password) //if a row is found check column 2 for password
{
destroy(); //destroy current window
if(queryModel->record(0).value(3).toString()== 1) //if id is equal to one log in as user
{
user.showMaximized();
}
else {
dbManager.showMaximized();
}
}
else {
qWarning("Wrong Password or Username");
}
}

Answer 1

I think your query is wrong. Instead of writing like this:
queryModel->setQuery("SELECT * FROM [User Database] WHERE Username= username"); //select the row of where the Username == username
You might want writing like this:
queryModel->setQuery(QString("SELECT * FROM [User Database] WHERE Username = '%1'").arg(username)); //select the row of where the Username == username
Why? Because you are writing a query, and you probably want to check against the user name entered, not the string "username". Also, don't forget apostrophes when comparing.
In order to find more information which might help with your problem, you should read Qt's documentation regarding its' classes. Also, it would be beneficial to take a look into the SQLite WHERE clause and how strings are represented when writing queries:
https://doc.qt.io/qt-5/qsqlquerymodel.html#setQuery
https://doc.qt.io/qt-5/qsqlquery.html#QSqlQuery-1
http://www.sqlitetutorial.net/sqlite-where/
https://www.sqlite.org/datatype3.html