500 Servlet Exception

com.keling.db.LoggedSQLException: 第 1 行: 'for_count_purpose' 附近有语法错误。
SQL: 
select count(*) from (select * from subjects where superiorId=0  for_count_purpose
	at com.keling.db.Link.query(Link.java:296)
	at com.keling.db.Link.returnObjects(Link.java:529)
	at com.keling.db.Link.returnObject(Link.java:552)
	at com.keling.db.Link.returnNumber(Link.java:569)
	at com.keling.db.Link.returnNumber(Link.java:645)
	at com.keling.db.Link.returnInt(Link.java:661)
	at com.keling.db.ext.PageSelector.getTotal(PageSelector.java:124)
	at com.keling.db.ext.PageSelector.getPages(PageSelector.java:98)
	at com.keling.db.ext.PageResult.getPages(PageResult.java:38)
	at com.keling.sp.ctrl.Pagi.classic(Pagi.java:69)
	at com.keling.sp.ctrl.Pagi.classic(Pagi.java:131)
	at _jsp._subject._index__jsp._jspService(subject/index.jsp:210)
	at com.caucho.jsp.JavaPage.service(JavaPage.java:61)
	at com.caucho.jsp.Page.pageservice(Page.java:578)
	at com.caucho.server.dispatch.PageFilterChain.doFilter(PageFilterChain.java:192)
	at com.caucho.server.webapp.WebAppFilterChain.doFilter(WebAppFilterChain.java:178)
	at com.caucho.server.dispatch.ServletInvocation.service(ServletInvocation.java:241)
	at com.caucho.server.http.HttpRequest.handleRequest(HttpRequest.java:268)
	at com.caucho.server.port.TcpConnection.run(TcpConnection.java:586)
	at com.caucho.util.ThreadPool$Item.runTasks(ThreadPool.java:690)
	at com.caucho.util.ThreadPool$Item.run(ThreadPool.java:612)
	at java.lang.Thread.run(Thread.java:619)