存储过程给予“折扣”基于X从今天的月份数量

Question

所以我的问题是，我必须制定一个程序，将产品表中的所有价格乘以0.8，如果产品没有售出X数量几个月。

目前，我似乎无法得到任何进一步的比这

GO 
CREATE PROC newprice(@numberofmonth int) 
AS 
BEGIN 
DECLARE @today datetime 
SET @today = GetDate() 
SELECT product.productid, product.name 
FROM orders JOIN orderitem on orderitem.orderid = orders.orderid 
      JOIN product on product.productid = orderitem.productid 
WHERE orders.orderdate > (SELECT DATEADD(month, -@numberofmonth, @today)) 

UPDATE product set price = price * 0.8 where 
END 

希望一切是足够透明的阅读，没有任何进一步的说明了解。我正在使用SQL Server。

Answer 1

我不明白你的问题completly.i只是假设你需要看看这个

GO CREATE PROC newprice(@numberofmonth int) 
AS 
BEGIN 
DECLARE @today datetime 
SET @today = GetDate() 
UPDATE product set price = price * 0.8 FROM orders JOIN orderitem on orderitem.orderid = orders.orderid JOIN product on product.productid = orderitem.productid WHERE orders.orderdate > 
(SELECT DATEADD(month, -@numberofmonth, @today)) 
END 

Answer 2

CREATE PROCEDURE newprice(@numberofmonth int) 
AS 
BEGIN 

UPDATE product 
SET price = price * 0.8 
FROM product 
JOIN orderitem on product.productid = orderitem.productid 
JOIN orders on orderitem.orderid = orders.orderid 
WHERE orders.orderdate > (DATEADD(month, -@numberofmonth, GETDATE())) 

END 

Answer 3

请检查如果它让你需要的东西：

DECLARE @today datetime 
SET @today = GetDate() 

Select * FROM product 
--UPDATE product SET price = price * 0.8 
WHERE not exists (
    SELECT product.productid, product.name 
    FROM orders 
    INNER JOIN orderitem on orderitem.orderid = orders.orderid 
    WHERE orders.orderdate > (SELECT DATEADD(month, -@numberofmonth, @today)))