请帮忙看下,我想实现按时间段统计用户发稿数,以下代码没有显示,看看问题出在哪里?

select top 12 a.userid,a.username,totalNum from ks_user a,(select inputer,count(*) as totalnum from ks_article where verific=1 and  AddDate>={ReqStr(StartDate)} and AddDate <={ReqStr(EndDate)} group by inputer)b where a.username=b.inputer and usertype=1 order by b.totalnum desc

AddDate是数据库里的日期,startdate enddate是日期控件选择的日期.