如何执行ms访问查询

Question

我有三个名为1的表：site_stock，2：item_add，3：stock_add。现在我想更新site_stock它的值应该是item_add初始余额和stock_add项目数量的总和我已尝试此查询但它给了我错误＆＃34;操作必须使用可更新查询＆＃34;

UPDATE site_stock
SET quantity = ((select sum(sa.quantity) from stock_add as sa where sa.item_code='J-110') +
                (select sum(ia.quantity) from item_add as ia where ia.item_code='J-110'))
WHERE item_code='J-110' and site_id=1;

Answer 1

UPDATE ((site_stock inner join item_add on site_stock.item_code=item_add.item_code) left join stock_add on site_stock.item_code=stock_add.item_code )  SET site_stock.quantity =(item_add.quantity + (iif(stock_add.quantity is null,0,stock_add.quantity))) WHERE  item_add.item_code=site_stock.item_code and site_stock.site_id=1;