select 
sum( case when convert(char(7),dateadd( month,-1,'出库日期' ),120) = convert(char(7),dDate,120) then iquantity else 0 end ),
sum( iquantity)
from Records where dDate < '出库日期' and cInvCode = '存货编码'

------解决方案--------------------

--上月出仓数量
select cWhName,SUM(iQuantity) from Records
where cInvCode='条件1存货编码'  
and	dDate>=convert(varchar(7),DATEADD(MONTH,-1,'条件2出库日期'),120)+'-01'
and dDate<dateadd(month,1,convert(varchar(7),DATEADD(MONTH,-1,'条件2出库日期'),120)+'-01')
group by cWhName
--累计出仓数量
select cWhName,SUM(iQuantity) from Records
where cInvCode='条件1存货编码'  
group by cWhName
如果cBusType（入库类型）“入库”、“出库”的区别，就在where后面加个即可。