用SQL进行地铁线路换乘查询

这代码是当初做课程作业时写出来的，过了几个月了现在看了看发现还挺不错的，说不定现在还写不出来了呢·~·。语法较为基础，都是简单的关键字，但是逻辑嵌套比较复杂，也用了大量的in，所以效率上可能不那么给列，不知道用来查公交速度如何~~~
SQL我写在了Java里，方便传参和二次换乘衔接，代码如下

package xiaolengzi;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;


public class Path {
    long startTime = System.currentTimeMillis();
    Connection con;// 创建一个数据库连接
    Connection con2;// 创建一个数据库连接，只创建一个会自动断开
    Statement sta0;// 创建预编译语句对象，最好是换成PreparedStatement吧
    Statement sta1;
    Statement sta2;
    String sql0;
    String sql1;
    String sql2;
    ResultSet rs0;
    ResultSet rs1;
    ResultSet rs2;
    List mid = new ArrayList();

    public static void main(String[] args) {
        new Path("古田一路", "街道口");
    }

    public Path(String start, String end) {
        try {
            Class.forName("com.mysql.jdbc.Driver");// 加载MySQL驱动程序
            String url = "jdbc:mysql://127.0.0.1:3306/Metro";
            String user = "xiaoleng";// 用户名,系统默认的账户名
            String password = "xiaoleng123";// 你安装时选设置的密码
            con = DriverManager.getConnection(url, user, password);// 获取连接
            con2 = DriverManager.getConnection(url, user, password);// 获取连接
            sta0 = con.createStatement();
            sta1 = con2.createStatement();
            sta2 = con2.createStatement();
            sql0 = "SELECT NAME FROM `METROSITE` WHERE BELONG in"
                    + "(SELECT BELONG FROM METROSITE WHERE `NAME` = '"+ start + "')" 
                    + "and `NAME` in(SELECT `NAME` FROM METROSITE WHERE BELONG in ("
                    + "SELECT BELONG FROM METROSITE WHERE `NAME` = '" + end + "'))";
            rs0 = sta0.executeQuery(sql0);
            while (rs0.next()) {
                mid.add(rs0.getString(1));
            }

            if (mid.size() == 0) {
                System.out.println("您选择的两个站之间无法通过一次换乘到达，请问需要换乘第二次吗？(默认YES)");
                sql1 = "SELECT `NAME` FROM `METROSITE` WHERE BELONG in"
                        + "(SELECT BELONG FROM METROSITE WHERE `NAME` = '" + start + "') "
                        + "and `NAME` in(SELECT `NAME` FROM METROSITE WHERE BELONG in("
                        + "SELECT BELONG FROM METROSITE WHERE BELONG not in"
                        + "(SELECT BELONG FROM METROSITE WHERE `NAME` = '" + start + "')));";
                rs1 = sta1.executeQuery(sql1);
                while (rs1.next()) {
                    sql2 = "SELECT `NAME` FROM `METROSITE` WHERE BELONG in"
                            + "(SELECT BELONG FROM METROSITE WHERE `NAME` = '" + end + "')"
                            + "and `NAME` in(SELECT `NAME` FROM METROSITE WHERE BELONG in("
                            + "SELECT BELONG FROM METROSITE WHERE BELONG not in"
                            + "(SELECT BELONG FROM METROSITE WHERE `NAME` = '" + end + "')))"
                            + "and `NAME` in(SELECT `NAME` FROM METROSITE WHERE BELONG in"
                            + "(SELECT BELONG FROM METROSITE WHERE `NAME` in"
                            + "(SELECT `NAME` FROM `METROSITE` WHERE BELONG in"
                            + "(SELECT BELONG FROM METROSITE WHERE `NAME` = '" + start + "')"
                            + "and `NAME` in(SELECT `NAME` FROM METROSITE WHERE BELONG in("
                            + "SELECT BELONG FROM METROSITE WHERE BELONG not in"
                            + "(SELECT BELONG FROM METROSITE WHERE `NAME` = '" + start + "'))))))"
                            + "and `NAME` in(SELECT `NAME` FROM METROSITE WHERE BELONG in"
                            + "(SELECT BELONG FROM METROSITE WHERE `NAME`='" + rs1.getString(1) + "'));";
                    rs2 = sta2.executeQuery(sql2);
                    while (rs2.next()) {
                        System.out.println("可换乘线路为：" + start + "————>" + rs1.getString(1) + "————>" + rs2.getString(1)
                                + "————>" + end);
                    }
                }
            } else {
                for (int i = 0; i < mid.size(); i++) {
                    System.out.println("可换乘线路为：" + start + "————>" + mid.get(i) + "————>" + end);
                }
            }
            long endTime = System.currentTimeMillis();
            System.out.println("计算完了!!!，耗时：" + (endTime - startTime) + "ms");
            con.close();con2.close();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }

}

关键的部分呢，就是那几个SQL语句了。
数据库的构造是这个样子的，是不是很简单啊

    private Integer id;  //当主键的

    private String name;  //地铁站名

    private Integer belong;  //属于几号线

效果演示：

票价这个功能Java后台搞定了，但是这个小项目里没弄，就没管它了
demo访问地址：之前用的腾讯云服务器到期了没续费~~看不了demo了T-T