我怎么能在SQL中做這個減法

Question

UPDATE parts 
SET    stock = (SELECT parts.stock - [item selection].quantity AS Expr1) 
FROM   parts 
       CROSS JOIN [item selection] 
WHERE  ( parts.part_type = @QuantityParameter ) 

我想要的是我想要的東西我做了一個新的訂單減去了客戶在庫存中購買的數量

Answer 1

在第一眼看我在查詢中看到代碼格式問題，試試這個：

UPDATE parts 
SET    stock = parts.stock - [item selection].quantity
From   parts 
       CROSS JOIN [item selection] 
WHERE  ( parts.part_type = @QuantityParameter )