How to retrieve data from Database ? and Display to JTable

write this code in below constructor :

DefaultTableModel model;
model = new DefaultTableModel(null,col);

        jTable1.setModel(model);

        int l2 = jTable1.getRowCount();
        while(l2>=1)
        {
            model.removeRow(0);
            l2 = l2-1;
        }