为什么这个SQL字符串不起作用？

dim ifHS
ifHS=request.Form("ifHS")
YearMonth=request.QueryString("YearMonth")
YearMonth2=request.QueryString("YearMonth2")
Dfdate=request.QueryString("Dfdate")
Dfdate2=request.QueryString("Dfdate2")
Worker=request.QueryString("Worker")
MeterNumber=request.QueryString("MeterNumber")
strwhere=""
strwhere2=""
if len(YearMonth)>=6 then strwhere=" HsDate>='"&YearMonth&"'"
if len(YearMonth2)>=6 then
if strwhere<>"" then
strwhere=strwhere&" and HsDate<='"&YearMonth2&"'"
else
strwhere=" HsDate<='"&YearMonth2&"'"
end if
end if

if len(Dfdate)>=6 then strwhere=strwhere&" DianfuDate>='"&Dfdate&"'"
if len(Dfdate2)>=6 then
if strwhere<>"" then
strwhere=strwhere&" and DianfuDate<='"&Dfdate2&"'"
else
strwhere=" DianfuDate<='"&Dfdate2&"'"
end if
end if

if UserNumber<>0 then
if strwhere<>"" then
strwhere=strwhere&" and UserNumber='"&UserNumber&"'"
else
strwhere=" UserNumber='"&UserNumber&"'"
end if
else
UserNumber=""
end if

if Worker<>"" then
if strwhere<>"" then
strwhere=strwhere&" and Worker='"&Worker&"'"
else
strwhere=" Worker='"&Worker&"'"
end if
else
Worker=""
end if

if MeterNumber<>"" then
if strwhere<>"" then
strwhere=strwhere&" and MeterNumber='"&MeterNumber&"'"
else
strwhere=" MeterNumber='"&MeterNumber&"'"
end if
else
MeterNumber=""
end if

if ifHS=1 then
strwhere2="where HsDate<>''"
elseif ifHS=2 then
strwhere2="where HsDate=''"
end if


if strwhere<>"" then
sql="select * from cqdf where "&strwhere&" order by ID Desc"
sql2="select sum(Total) from cqdf where "&strwhere&" and HsDate<>''"
sql3="select sum(Total) from cqdf where "&strwhere
sql4="select sum(WAmount) from cqdf where "&strwhere&" and HsDate<>''"
sql5="select sum(WAmount) from cqdf where "&strwhere
sql6="select sum(Amount) from cqdf where "&strwhere&" and HsDate<>''"
sql7="select sum(Amount) from cqdf where "&strwhere
else
sql="select * from cqdf order by ID Desc"
sql2="select sum(Total) from cqdf where HsDate<>''"
sql3="select sum(Total) from cqdf "
sql4="select sum(WAmount) from cqdf where HsDate<>''"
sql5="select sum(WAmount) from cqdf "
sql6="select sum(Amount) from cqdf where HsDate<>''"
sql7="select sum(Amount) from cqdf "
end if
if strwhere2<>"" then
sql="select * from cqdf "&strwhere2&" order by ID Desc"
sql2="select sum(Total) from cqdf "&strwhere2
sql3="select sum(Total) from cqdf "&strwhere2
sql4="select sum(WAmount) from cqdf "&strwhere2
sql5="select sum(WAmount) from cqdf "&strwhere2
sql6="select sum(Amount) from cqdf "&strwhere2
sql7="select sum(Amount) from cqdf "&strwhere2
end if
%>

<select name="ifHS" id="ifHS">
<option value="0" >所有</option>
<option value="1" >已回收</option>
<option value="2" >未回收</option>
</select>

为什么strwhere2不起作用？而strwhere可以正常筛选？