SQL connection closure problem.

What i am trying to do is to make a dialog where the user enters the data needed for a connection and finally makes the connection.

I have two buttons.

The first button should check whether a connection has already been made and if not start a new connection. If a connection has already been made then write a message saying connection already open.

The second button should disconnect the database.

The problem is that I cannot disconnect the database and that instead of checking whether one is already open it creates another one each time i ress the button. (and I receive the relevant error code form the command line).

I have attached the code. I cant figure out what's wrong on my own.Your help is much appreciated.

Many thanks in advance.

Code:

#include "database.h"
 
#include <QtGui>
#include <QApplication>
 
int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    database w;
    w.show();
    return a.exec();
}

Code:

#ifndef DATABASE_H
#define DATABASE_H
 
#include <QtGui/QWidget>
#include <QtSql>
#include "ui_database.h"
class A {
	public:
	QString pinakas;
	QString onoma;
	QString kodikos;
};
 
class database : public QWidget
{
    Q_OBJECT
 
public:
    database(QWidget *parent = 0);
    ~database();
 
 
public slots:
	void sindesou();
	void aposindesou();
 
private:
    Ui::databaseClass ui;
    A ena;
    QSqlDatabase db;
 
};
 
#endif // DATABASE_H

database.cpp:

Code:

#include "database.h"
#include <QtSql>
#include <QMessageBox>
#include <QSqlDatabase>
#include <QSqlError>
#include <QSqlQuery>
#include <QApplication>
#include <QCoreApplication>
#include <QDebug> 
#include "ui_database.h"
 
 
 
database::database(QWidget *parent)
    : QWidget(parent)
{
	ui.setupUi(this);
	connect(ui.sindesi, SIGNAL(clicked()), this, SLOT(sindesou()));
	connect(ui.aposindesi, SIGNAL(clicked()), this, SLOT(aposindesou()));
 
	//QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
}
 
void database::sindesou() {
	    ena.pinakas = ui.pinakas->text();
	    ena.onoma = ui.onoma->text();
	    ena.kodikos = ui.kodikos->text();
	    if (!db.open()) {
	    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
	    db.setDatabaseName(ena.pinakas);
	    db.setUserName(ena.onoma); 
	    db.setPassword(ena.kodikos); 
	    db.setHostName("127.0.0.1");
	    db.setPort( 3306 );                     
	    if (!db.open()) {
	        ui.katastasi->setText("Not connected");
	    } else {
	    	ui.katastasi->setText("connected");
	    }
	    }
	    else {
	    	ui.katastasi->setText("It has already been connected");
	    }
	    };
 
 
void database::aposindesou() {
	db.close();///<<--- This doesnt close the connection
}
 
database::~database()
{
 
}