QSql - "Error opening database", "unable to open database file"

[SykeS]

I have the following code:


#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtSql>
#include <QDebug>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
QSqlDatabase m = QSqlDatabase::addDatabase("QSQLITE");
m.setDatabaseName(":baza:");
bool ok = m.open();
if (ok)
{
qDebug() << "connected" << endl;
}
else
{
qDebug() << "not Connected " << endl;
qDebug() << QSqlDatabase::drivers() << endl;
qDebug() << m.lastError();
}

}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::changeEvent(QEvent *e)
{
QMainWindow::changeEvent(e);
switch (e->type()) {
case QEvent::LanguageChange:
ui->retranslateUi(this);
break;
default:
break;
}
}


and it's returning:


not Connected

("QSQLITE", "QODBC3", "QODBC")

QSqlError(-1, "Error opening database", "unable to open database file")

What's wrong?

[tbscope]

Colons are forbidden in filenames

[SykeS]

Hmmm.... It works, but... How to define temporary in-memory database? In QT Examples there is something like this:

QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName(":memory:");
And it works, but not in my program :)

[tbscope]

What happens if you leave the database name empty. That should be the same as :memory: according to the SQLite docs.

Anyway: the ":memory:" string is special. I don't know how Qt handles that, if at all.
In any normal case, the databasename for a SQLite database is also the filename. And you can not have a colon in a filename.

[JD2000]

Not something like, but exactly like - to quote from the docs
SQLite also supports in-memory databases, simply pass ":memory:" as the database name.

[SykeS]

Thanks a lot!

But now I have the following code:

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include <QtSql>
#include <QDebug>
#include <QMessageBox>
#include <QSqlTableModel>

MainWindow::MainWindow(QWidget *parent) :
QMainWindow(parent),
ui(new Ui::MainWindow)
{
ui->setupUi(this);
initDatabase();
QSqlTableModel model;

model.setTable("person");
model.select();

model.setHeaderData(1, Qt::Horizontal, QObject::tr("First name"));
model.setHeaderData(2, Qt::Horizontal, QObject::tr("Last name"));
model.setHeaderData(0, Qt::Horizontal, QObject::tr("ID"));
ui->tableView->setModel(&model);
qDebug() << model.lastError();
}

MainWindow::~MainWindow()
{
delete ui;
}

void MainWindow::changeEvent(QEvent *e)
{
QMainWindow::changeEvent(e);
switch (e->type()) {
case QEvent::LanguageChange:
ui->retranslateUi(this);
break;
default:
break;
}
}

bool MainWindow::initDatabase()
{
QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
db.setDatabaseName(":memory:");

if(!db.open()){
QMessageBox::critical(this, tr("Błąd bazy danych"), tr("Nie można połączyć się z bazą danych."
"\n%1").arg("test"));
return false;
}

QSqlQuery query;
query.exec("create table person (id int primary key, "
"firstname varchar(20), lastname varchar(20))");
query.exec("insert into person values(101, 'Danny', 'Young')");
query.exec("insert into person values(102, 'Christine', 'Holand')");
query.exec("insert into person values(103, 'Lars', 'Gordon')");
query.exec("insert into person values(104, 'Roberto', 'Robitaille')");
query.exec("insert into person values(105, 'Maria', 'Papadopoulos')");
return true;
}


and it prints window like in attachment. Why?

[JD2000]

You need
ui->tableView->show(); at the end of the MainWindow constructor to actually see the tableview.

[ChrisW67]

"model" goes out of scope at the end of the constructor leaving nothing for the table view to show.

[SykeS]

@JD2000 - I use Qt Creator.


"model" goes out of scope at the end of the constructor leaving nothing for the table view to show.
What is the solution?

[JD2000]

Add this to mainwidow.h

private:
QSqlTableModel *model;