Java/SQL Removing double data

[Subhero]

I know this might seem like a simple query problem [and it probably is but not for me :D].

The problem is the following that using the DISTINCT method in the query does not remove the double data. I tried using DISTINCT only on gemeente, but then the data does not show up in my ComboBox.

The point is is that I remove the double data from the gemeente column, which contains a bunch of towns and their postal codes. Then I need to list those towns in a ComboBox but applying DISTINCT to gemeente only works as a query in SQL, but then I do not see the data in my combobox.

public Vector<jstageGemeente> getjStageGemeente() {

        Statement stmt = null;
        ResultSet rs = null;
        jstageGemeente gemeente = null;
        Vector <jstageGemeente> resultaat = new Vector<jstageGemeente>();

        try {
            stmt = connection.createStatement();
            rs = stmt.executeQuery("SELECT DISTINCT id, postcode, gemeente FROM jstageGemeente ORDER BY gemeente");

            while (rs.next()) {
                gemeente = new jstageGemeente();
                gemeente.setId(rs.getInt(1));
                gemeente.setPostcode(rs.getInt(2));
                gemeente.setGemeente(rs.getString(3));
                resultaat.add(gemeente);
            }
        }

StudentFrame that loads the data into the combobox

public class StudentFrame extends JFrame implements ActionListener {

    private Container content;
    private JPanel topLeft, topRight, bottomLeft, bottomRight;
    private JComboBox gemeentenBox, sectorBox, soortBox;
    private JTextField aantalVeld;
    private JButton zoekenButton;

    private DAjstageLogin daLogin = null;
    private DAjstageBedrijf daBedrijf = null;
    private DAjstageGemeente daGemeente = null;
    private DAjstageKeuze daKeuze = null;
    private DAjstageSector daSector = null;
    private DAjstageSoort daSoort = null;
    private DAjstageStudent daStudent = null;
    private DAjstageOpdracht daOpdracht = null;

    public StudentFrame(DAjstageBedrijf daBedrijf, DAjstageKeuze daKeuze, DAjstageGemeente daGemeente, DAjstageSector daSector, DAjstageOpdracht daOpdracht, DAjstageSoort daSoort, DAjstageStudent daStudent, DAjstageLogin daLogin)
                    throws Exception {

        this.daGemeente = daGemeente;
        this.daSector = daSector;
        this.daOpdracht = daOpdracht;
        this.daStudent = daStudent;
        this.daKeuze = daKeuze;
        this.daLogin = daLogin;
        this.daSoort = daSoort;

        this.setLocation(150,150);
        setTitle("Welkom");
        setSize(1000,750);
        opbouwScherm();
        addWindowListener(new VensterHandler());
        setVisible(true);
        this.setResizable(false);

    }


    public void opbouwScherm(){
        content = getContentPane();
        content.setLayout(null);

        JComboBox gemeentenBox = new JComboBox(daGemeente.getjStageGemeente());
        gemeentenBox.insertItemAt("geen voorkeur", 0);
        JComboBox sectorBox = new JComboBox(daSector.getjStageSector());
        sectorBox.insertItemAt("geen voorkeur", 0);
        JComboBox soortBox = new JComboBox(daSoort.getjStageSoort());
        soortBox.insertItemAt("geen voorkeur", 0);
        JTextField aantalVeld = new JTextField();
        JButton zoekenButton = new JButton("Zoek");
        JLabel gemeentenLabel = new JLabel("Locatie bedrijf:");
        JLabel aantalLabel = new JLabel("Werkzame informatici:");
        JLabel sectorLabel = new JLabel("Sector stagebedrijf:");
        JLabel soortLabel = new JLabel("Soort stage:");

        //comboboxen
        gemeentenBox.setBounds(5, 30, 150, 20);
        sectorBox.setBounds(160, 30, 325, 20);
        soortBox.setBounds(495, 30, 140, 20);
        aantalVeld.setBounds(625, 30, 135, 20);

        //labels
        gemeentenLabel.setBounds(5,10,120,20);
        sectorLabel.setBounds(160,10,120,20);
        soortLabel.setBounds(495,10,120,20);
        aantalLabel.setBounds(625,10,135,20);

        //buttons
        zoekenButton.setBounds(800,30,80,20);

        content.add(gemeentenBox);
        content.add(sectorBox);
        content.add(soortBox);
        content.add(aantalVeld);
        content.add(gemeentenLabel);
        content.add(sectorLabel);
        content.add(soortLabel);
        content.add(aantalLabel);
        content.add(zoekenButton);

    }

[chyrl]

Well this thread doesn't really belong to this location.
It must be placed in the database section.

Anyways,
I think I have solved your problem.
You can't have two columns to "DISTINCT". You must only select one column.
Or you may add a "GROUP BY" phrase to which column you must have the "DISTINCT" phrase working.

The GUI code on the other hand, is perfectly coded.

[Tolls]

Well this thread doesn't really belong to this location.
It must be placed in the database section.

Anyways,
I think I have solved your problem.
You can't have two columns to "DISTINCT". You must only select one column.

Yes you can.
I've just done it in MySQL.

OP: You're not eating an exception somewhere are you? Though I can't think why that would give you an exception if the one without the DISTINCT doesn't.