create table aa(item varchar(100),zt varchar(100))
go

insert into aa 
select item,case when td018 = 'Y' then TD018为采购数量 else 0 end - TD015为供应商已交数量
from PURTD

go


drop table aa

------解决方案--------------------
SQL code
create table #aa(item varchar(20),zt varchar(20));
go

insert #aa(item,zt) select td004,TD018-TD015t from purtd where td016 = 'N' and td018 = 'Y'

------解决方案--------------------
临时表有全局和局部的，当是局部时仅存在于当前会话，会话结束后临时表自动清除

------解决方案--------------------
SQL code
create table #aa(item varchar(100),zt varchar(100))
go

insert into #aa 
select item, TD08 - TD015
from PURTD
when td018 = 'Y' 
go


drop table #aa