十二大战结局是什么:JSP 向数据库表插入数据出错

在用JSP 向数据库表插入数据出错
[Microsoft][ODBC Microsoft Access Driver] INSERT INTO 语句的语法错误。 代码如下：
<%@ page contentType="text/html;charset=GB2312" %>
<%@ page import="java.sql.*" %>
<%!
public String codeToString(String str)
{
String s=str;
try
{
byte tempB[]=s.getBytes("ISO-8859-1");
s=new String(tempB);
return s;
}
catch(Exception e)
{
return s;
}
}
%>

<%
String tid=codeToString(request.getParameter("id"));
String ttype=codeToString(request.getParameter("type"));
String tnum=codeToString(request.getParameter("num"));
String tlevel=codeToString(request.getParameter("level"));

String sql=null;

sql="INSERT into typetable(id,type,num,level) values(tid,ttype,tnum,tlevel)";
try
{
Connection con;
Statement stmt;
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
//jspdb是odbc数据源的名称
con=DriverManager.getConnection("jdbc:odbc:mydb","","");
stmt=con.createStatement();
stmt.executeUpdate(sql);
con.close();
catch(Exception e){
out.println(e.getMessage());
}

//response.sendRedirect("dbshow.jsp");
%>