关于 order by desc的问题

关于 order by desc的问题
sql="select * from [content] where Nclassid="&cstr(anclassid)
请问这句,在什么地方加入 order by desc
sql="select * from [content] where Nclassid="&cstr(anclassid)& " order by desc
这个不行,出错