如何检查某三列是否已经存在？

import java.sql.*;

public class CheckColumnsExistence {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/database_name";
        String username = "username";
        String password = "password";

        try {
            // 连接数据库
            Connection connection = DriverManager.getConnection(url, username, password);

            // 编写查询语句
            String query = "SELECT * FROM table_name WHERE column1=value1 AND column2=value2 AND column3=value3";

            // 执行查询语句
            Statement statement = connection.createStatement();
            ResultSet resultSet = statement.executeQuery(query);

            // 处理查询结果
            if (resultSet.next()) {
                System.out.println("某三列已经存在");
            } else {
                System.out.println("某三列不存在");
            }

            // 关闭连接
            resultSet.close();
            statement.close();
            connection.close();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}