~~~~~~~~~请大家帮帮小弟，过来看看,马上给分~~~~~~~~

Question

update Web_inventory_limit set quantity_sell=2*Promotion_item.item_number
from Promotion_item
where Promotion_item.promotionID=1  and Web_inventory_limit.whcode=5
and Web_inventory_limit.item_no    =Promotion_item.item_no

Answer 1

update Web_inventory_limit set quantity_sell=2*Promotion_item.item_number
from Promotion_item
where Web_inventory_limit.item_no=Promotion_item.item_no and Promotion_item.promotionID=1 and Web_inventory_limit.whcode=5

Answer 2

我这样写的，不知道对吗
update web_inventory_limit set quantity_sell=quantity_sell+p.item_number
from web_inventory_limit w inner join promotion_item p on w.item_no=p.item_no
where w.wh_code=5 and p.promotionid='1'

Answer 3

update Web_inventory_limit set quantity_sell=
(select 2*Promotion_item.item_number from Promotion_item where 
Promotion_item.promotionID=1 and Web_inventory_limit.whcode=5)

Answer 4

update Web_inventory_limit 
set quantity_sell=2*a.item_number
from Promotion_item a
where Web_inventory_limit.item_no=a.item_no and a.promotionID=1 and Web_inventory_limit.whcode=5