请帮忙解释一下这段代码

Question

<%
String Modify_Id=request.getParameter("modifyid");
if (Modify_Id!=null)
{
sql="select * from 公告 where 公告id="+Modify_Id;
rs=stmt.executeQuery(sql);
while(rs.next())
{
     Not_Title=rs.getString("公告标题");
 Not_Content=rs.getString("公告内容");
    Submit_Button="修改";
}}else
{
Modify_Id="0";
Not_Title="";
Not_Content="";
Submit_Button="新增";
}
%>请帮忙解释一下这段代码，给下每句话的注释，十分感激！

Answer 1

<%
String Modify_Id=request.getParameter("modifyid");//从REQUEST中获取modifyid，赋值给Modify
if (Modify_Id!=null)                                //判断Modify是不是存在        如果存在就可以修改
{
sql="select * from 公告 where 公告id="+Modify_Id;        //这个基础的没法解释
rs=stmt.executeQuery(sql);                                //执行上边SQL返回结果集
while(rs.next())                                           //遍历整个结果集
{
     Not_Title=rs.getString("公告标题");                     //从结果集中获取数据
 Not_Content=rs.getString("公告内容");
    Submit_Button="修改";
}}else                                                                           //如果不存在就增加
{
Modify_Id="0";
Not_Title="";
Not_Content="";
Submit_Button="新增";
}
%>