今天完成的事情：完善了改,删,查的功能

以下是新增模块的代码

    //更改(升级)数据:暂时只支持修改Sqq

    public int update(long Sqq,String Sname) {

    int result = 0;

        try {

            Class.forName("com.mysql.jdbc.Driver");

        } catch (ClassNotFoundException e) {

            e.printStackTrace();

        }

    String sql = "update registration set Sqq=? where Sname=?";

    try (Connection conn= DriverManager.getConnection(url,un,pw); 

          PreparedStatement ps = conn.prepareStatement(sql);){

             ps.setLong(1, Sqq);

             ps.setString(2, Sname);

             result = ps.executeUpdate();

    }catch(SQLException e){

          e.printStackTrace();

    }

    return result;

    }

    //删除数据,根据Sname

    public int delete(String Sname) {

    int result = 0;

        try {

            Class.forName("com.mysql.jdbc.Driver");

        } catch (ClassNotFoundException e) {

            e.printStackTrace();

        }

String sql = "delete from registration where Sname=?";

    try (Connection conn = DriverManager.getConnection(url,un,pw); 

          PreparedStatement ps = conn.prepareStatement(sql);){

             ps.setString(1, Sname);

             result = ps.executeUpdate();

    }catch(SQLException e) {

    e.printStackTrace();

    }

    return result;

    }

    //查询数据

    public void select(String Sname) {

        try {

            Class.forName("com.mysql.jdbc.Driver");

        } catch (ClassNotFoundException e) {

            e.printStackTrace();

        }

String sql = "select * from registration where Sname = '"+Sname+"'";

    try(Connection conn = DriverManager.getConnection(url,un,pw);

          Statement info = conn.createStatement();

          ResultSet rs = info.executeQuery(sql)) {

        while(rs.next()) {

              System.out.println(rs.getString("id")+" "+rs.getString("Sname")

              +" "+rs.getString("crate_at")+" "+rs.getString("update_at"));

        }

    }catch(SQLException e){

    e.printStackTrace();

    }

    }

明天计划的事情：解决时间,crate_at和update_at的问题,结束DAO模块的任务

遇到的问题： Statement和preparedStatement相比,代码书写和阅读确实不够直观,"'这种双引号套单引号太繁琐了

收获：即将完成DAO模块,继续向完成任务的目标前进