如何从查询关系数据库中获取CSV字符串？

import csv
import sqlite3

def fetch_csv_from_db(db_path, table_name):
    conn = sqlite3.connect(db_path)
    cursor = conn.cursor()
    cursor.execute(f"SELECT * FROM {table_name}")
    
    # 获取列名
    columns = [description[0] for description in cursor.description]
    
    # 创建CSV字符串
    csv_data = csv.writer(open('output.csv', 'w', newline='', encoding='utf-8'))
    csv_data.writerow(columns)
    
    for row in cursor.fetchall():
        csv_data.writerow(row)
    
    conn.close()
    return 'output.csv'

# 使用示例
csv_file_path = fetch_csv_from_db('example.db', 'users')
print(f"CSV文件已生成：{csv_file_path}")

import java.io.FileWriter;
import java.io.IOException;
import java.sql.*;

public class DatabaseToCSV {
    public static void main(String[] args) {
        String url = "jdbc:mysql://localhost:3306/mydatabase";
        String user = "username";
        String password = "password";
        String table = "users";

        try (Connection conn = DriverManager.getConnection(url, user, password);
             Statement stmt = conn.createStatement();
             ResultSet rs = stmt.executeQuery("SELECT * FROM " + table);
             FileWriter fw = new FileWriter("output.csv")) {

            ResultSetMetaData rsmd = rs.getMetaData();
            int columnCount = rsmd.getColumnCount();

            // 写入列名
            for (int i = 1; i <= columnCount; i++) {
                fw.append(rsmd.getColumnName(i));
                if (i < columnCount) {
                    fw.append(",");
                }
            }
            fw.append("\n");

            // 写入数据行
            while (rs.next()) {
                for (int i = 1; i <= columnCount; i++) {
                    fw.append(rs.getString(i));
                    if (i < columnCount) {
                        fw.append(",");
                    }
                }
                fw.append("\n");
            }
        } catch (SQLException | IOException e) {
            e.printStackTrace();
        }
    }
}