当表包含NULL值时，如何使用joins将数据从DB添加到Java Swing中的jTable？

import javax.swing.*;
import javax.swing.table.DefaultTableModel;
import java.sql.*;

public class Main {
    public static void main(String[] args) {
        // 创建数据库连接
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String username = "root";
        String password = "password";
        try (Connection connection = DriverManager.getConnection(url, username, password)) {
            // 执行SQL查询语句
            String sql = "SELECT t1.column1, t2.column2 FROM table1 t1 INNER JOIN table2 t2 ON t1.id = t2.id";
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(sql);

            // 创建TableModel对象
            DefaultTableModel tableModel = new DefaultTableModel();

            // 添加列名
            tableModel.addColumn("Column 1");
            tableModel.addColumn("Column 2");

            // 遍历结果集并添加数据到TableModel
            while (resultSet.next()) {
                Object[] rowData = new Object[2];
                rowData[0] = resultSet.getString("column1");
                rowData[1] = resultSet.getString("column2");

                // 处理NULL值
                if (resultSet.wasNull()) {
                    rowData[0] = "N/A";
                }

                tableModel.addRow(rowData);
            }

            // 创建JTable并设置数据模型
            JTable jTable = new JTable(tableModel);

            // 创建一个滚动面板，并将JTable放入其中
            JScrollPane scrollPane = new JScrollPane(jTable);

            // 创建一个窗口，并将滚动面板放入其中
            JFrame frame = new JFrame();
            frame.add(scrollPane);
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.pack();
            frame.setVisible(true);

        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}