这sql语句是个神马情况，是hibernate配置还是………………求指点

public List<String> getSignupEventId(int attendeeId, int conferenceId) {
List<String> list = null;

String sql = "SELECT  s.event_id FROM exhibit AS e"
+ " Left Join followup_request AS fr ON fr.exhibit_id = e.id AND fr.requesting_attendee_id ="
+ attendeeId + " WHERE e.conference_id =" + conferenceId;
list = getSQLFrameList(sql);


if (list.size() > 0) {
return list;
} else {
return null;
}错误信息：org.springframework.dao.InvalidDataAccessResourceUsageException: could not execute query; SQL [SELECT  s.event_id FROM exhibit AS e Left Join followup_request AS fr ON fr.exhibit_id = e.id AND fr.requesting_attendee_id =4 WHERE e.conference_id =1]; nested exception is org.hibernate.exception.SQLGrammarException: could not execute query
at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:629)
at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:411)
at org.springframework.orm.hibernate3.HibernateTemplate.executeFind(HibernateTemplate.java:343)
at com.confpal.common.CommonFrameHiberbateDaoImpl.getSQLFrameList(CommonFrameHiberbateDaoImpl.java:88)
at com.confpal.dao.exe.ExhibitorDAOImpl.getSignupEventId(ExhibitorDAOImpl.java:78)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:307)
at org.springframework.aop.framework.ReflectiveMethodInvocation.invokeJoinpoint(ReflectiveMethodInvocation.java:183)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:108)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
at $Proxy9.getSignupEventId(Unknown Source)
at com.confpal.action.exhibitor.GetExhibitorListAction.getExhibitorList(GetExhibitorListAction.java:47)
at com.confpal.action.ExhibitorMainAction.forward(ExhibitorMainAction.java:24)
at com.confpal.servlet.MainServlet.doPost(MainServlet.java:72)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:306)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at com.confpal.common.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:26)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:244)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:240)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:161)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:164)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:550)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:380)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:243)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:188)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:166)
at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:288)
at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)