sql存储过程，减去或加到值 [英] sql stored procedure, subtract or add to value

问题描述

也许我对在Google中搜索的内容有些不解.

我的问题是这样定义的:
我有桌子在切断. 2列:productNr，

Maybe i have a little brainfreeze on what to search for in google.

My question is defined like this:
I have table at sever. 2 columns: productNr,

curQuantity<br />

在用户决定增加或减少此数量之后，我将通过该程序快速对该表进行更改.
我们当前的设置是这样的.

Troughout the day i have program which makes rapid changes to this table after user has decided to add or subtract to this amount.
Our current setup is like this.

Select-query to get curQuantity.
newQuantity = curQantity + (added or subtractet)
update-query to set newQantity.

我当时想应该可以在一个sql表达式中做到这一点?
从而提高了我们程序的效率.

I was thinking that this should be possible to do in one sql expression?
And therefor improve the efficiency of our program.

推荐答案

是:

DECLARE @OrigQuantity INT
SELECT TOP 1 @OrigQuantity = curQuantity FROM Products WHERE Id=3
UPDATE Products SET curQuantity = @OrigQuantity - 2 WHERE Id=3
SELECT @OrigQuantity 

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