一个关于jsp中的sql 语句 like 的问题急等解决！！！！！！

我有一段程序是关于 jsp中的sql语句的
程序如下<%
String getPage=request.getParameter("pageId").trim();
if(getPage.compareTo("-1")==0)
{
//分页准备工作，保存分页信息
Page myPage=new Page();
String bookname=request.getParamer("bookname").trim();
String author=request.getParameter("author").trim();
String nameSelect="";
String authorSelect="";
if(bookname.compareTo("")!=0) nameSelect="bookname like '%"+bookname+"%'";
if(author.compareTo("")!=0) authorSelect="author like '%"+author+"%'";

byte[] tmpbyte=nameSelect.getBytes("ISO8859_1");
nameSelect=new String(tmpbyte);
tmpbyte=authorSelect.getBytes("ISO8859_1");
authorSelect=new String(tmpbyte);

if(authorSelect.compareTo("")!=0&&nameSelect.compareTo("")!=0)
nameSelect=" and "+nameSelect;
String sql="select pid from book where";
sql=sql+authorSelect+nameSelect+" order by pid desc";
//sql是生成的查询语句
session.putValue("authorSelect",authorSelect);
session.putValue("nameSelect",nameSelect);
ResultSet rs=db.executeQuery(sql);

myPage.recordCount=0;
myPage.pageSize=10;
myPage.pageCount=0;
myPage.pageId=1;

Vector idList=new Vector();
getPage="1";
while(rs.next())
{
myPage.recordCount++;
if(myPage.recordCount==myPage.pageSize)
{
myPage.pageCount++;
idList.addElement(rs.getString("pid"));
myPage.recordCount=0;
}
}

if(myPage.recordCount!=0)
myPage.pageCount++;
myPage.recordCount+=(myPage.pageCount-1)*myPage.pageSize;
rs.close();
session.putValue("idList",idList);
session.putValue("myPage",myPage);
}
%>

但是运行时，总是报错, 说是在 like 关键字附近有语法错误但我找不出哪位高手请帮忙！！！