SQL Server中的错误更新

更新查询可以工作，但不正确

有什么问题

UPDATE Orders
SET discount = 10
WHERE EXISTS (SELECT C.discount 
              FROM Orders AS C
              JOIN OrderItems AS O ON C.orderID = O.orderID
              WHERE (C.dateOrder BETWEEN '01.07.2013' AND GETDATE()) 
              GROUP BY C.discount
              HAVING COUNT(O.orderID) > 1) 

这本身就是有效的

SELECT C.discount 
FROM Orders AS C 
JOIN OrderItems AS O ON C.orderID = O.orderID
WHERE (C.dateOrder BETWEEN '01.07.2013' AND GETDATE()) 
GROUP BY C.discount
HAVING COUNT(O.orderID) > 1

---

结果是正确的

我想这可能会做你想做的事-但我猜你没有完全理解你想做什么

UPDATE C SET
  discount = 10
FROM ORDERS C
WHERE C.dateOrder between '01.07.2013' and GETDATE()
-- Updating only orders with an existing discount
AND C.discount IS NOT NULL
-- And with more than 1 order line
AND (
  SELECT COUNT(*)
  FROM OrderItems AS O 
  WHERE O.orderID = C.orderID
) > 1 

---

我想这可能会做你想做的事——但我猜你并不完全了解你想做什么

UPDATE C SET
  discount = 10
FROM ORDERS C
WHERE C.dateOrder between '01.07.2013' and GETDATE()
-- Updating only orders with an existing discount
AND C.discount IS NOT NULL
-- And with more than 1 order line
AND (
  SELECT COUNT(*)
  FROM OrderItems AS O 
  WHERE O.orderID = C.orderID
) > 1 

---

“不正确”的实际含义是什么？您似乎没有引用您在exists子句中更新的表…我们不知道您试图实现什么，因此您需要解释这一点，以便我们了解它是如何不起作用的。查询显示两列。更新更新了整个表，请显示一些示例数据和预期结果。并尝试用文字解释，例如“我想用折扣更新所有订单，并用多个订单行更新10%的新折扣”。什么是“不正确”的实际含义？您似乎没有引用您在exists子句中更新的表格…我们不知道您试图实现什么，所以你需要解释一下，这样我们才能理解它是如何不起作用的。更新更新了整个表，请显示一些示例数据和预期结果。并尝试用文字解释，例如“我想用折扣更新所有订单，并使用多个订单行以获得10%的新折扣”。