改成
sql="select * from tbl_secondDir where PARENT_ID in("
+"select FIR_ID from tbl_firstDir where PARENT_ID="
+ request.getParameter("id")+")";
sql="select * from tbl_secondDir where PARENT_ID in("
+"select FIR_ID from tbl_firstDir where PARENT_ID="
+ request.getParameter("id")+")";
+"select FIR_ID from tbl_firstDir where PARENT_ID="
+ "request.getParameter("id")+")";
request.getParameter()得来的是String型的,你那个PARENT_ID是什么型的啊?