sql语句出错

[pangxiaoya]

目标是这样的统计starttime至endtime时间段内worktime的总和，标记字段finishdate在表sGONGXUORDERSHEETTRACE中，worktime是表DJ11PROCLAYOUT中的字段。我首先查询sGONGXUORDERSHEETTRACE中finishdate落在该时间段内的所有记录，然后根据某几个字段的值查找表DJ11PROCLAYOUT中的worktime，最后再求和，现在想用一个查询语句来完成，我写的sql语句如下，但是出错请大家指点一下，谢谢！
strsql="SELECT sum(DJ11PROCLAYOUT.WORKTIME) as worktimesum FROM DJ11PROCLAYOUT,sGONGXUORDERSHEETTRACE WHERE (DJ11PROCLAYOUT.PLANETYPE=sGONGXUORDERSHEETTRACE.PLANETYPE and DJ11PROCLAYOUT.PARTDWGNO=sGONGXUORDERSHEETTRACE.PARTDRAWINGID and DJ11PROCLAYOUT.PROCID=sGONGXUORDERSHEETTRACE.GONGXUID and sGONGXUORDERSHEETTRACE.finishdate between to_date('"&starttime&"','yyyy-mm-dd') and to_date('"&endtime&"','yyyy-mm-dd'))"