private void deleteActionPerformed(java.awt.event.ActionEvent evt) {

        try{
            Connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db", "root", "lego");
            Statement st = con.createStatement();
            DefaultTableModel model = (DefaultTableModel) table.getModel();

            int row = table.getSelectedRow();
            String value = (table.getModel().getValueAt(row, 0).toString());
            System.out.println("value = "+value);
            String query = "delete from db.study where name = '"+value+"';";
            PreparedStatement pst = con.prepareStatement(query);
            pst.executeUpdate();

            String sql = "select name,unit,comments from db.study where subject='"+sub+"' ORDER BY unit;";
            ResultSet rs = st.executeQuery(sql);

            table.setModel(DbUtils.resultSetToTableModel(rs));

        } catch(Exception e){
            System.out.println(e);
        }

    }