SQL 更新代码 'Where exisits' 未按预期运行

Question

我试图制作一些 SQL 更新代码，用 where exists 子句向注释字段添加一行，但它不断更新 table 中的每条记录，我不确定我在做什么搞砸了哈哈。如果您在下面的代码中看到我的错误并且可以帮助我，非常感谢。

UPDATE Orders
SET notes = 'Basic Confirmation Issued by TaskCentre: ' + CONVERT(varchar(10),getdate(),121)
WHERE EXISTS (SELECT  * 
FROM  Orders INNER JOIN Order_Lines ON orders.ORDER_NUMBER = Order_Lines.ORDER_NUMBER 
WHERE Orders.ORDER_DATE >= '20150630 00:00:00' 
AND Order_Lines.PRODUCT_CODE LIKE '15CONF%%' 
AND Orders.Email > ' ')

Answer 1

问题是您的第一个查询（更新）与第二个查询无关。因此，如果有任何结果，您基本上是在更新我的所有订单：

SELECT  * 
FROM  Orders INNER JOIN Order_Lines ON orders.ORDER_NUMBER = Order_Lines.ORDER_NUMBER 
WHERE Orders.ORDER_DATE >= '20150630 00:00:00' 
AND Order_Lines.PRODUCT_CODE LIKE '15CONF%%' 
AND Orders.Email > ' '

您需要以第一个与第二个关联的方式重写您的查询。或者您还可以做的是，不要使用 * 作为您的 select、return ID。然后更新第一个查询的 WHERE 子句以在第二个查询中搜索键，类似于：

UPDATE Orders
SET notes = 'Basic Confirmation Issued by TaskCentre: ' + CONVERT(varchar(10),getdate(),121)
WHERE order_number IN (SELECT  ORDER_NUMBER 
FROM  Orders INNER JOIN Order_Lines ON orders.ORDER_NUMBER = Order_Lines.ORDER_NUMBER 
WHERE Orders.ORDER_DATE >= '20150630 00:00:00' 
AND Order_Lines.PRODUCT_CODE LIKE '15CONF%%' 
AND Orders.Email > ' ')

你需要仔细检查密钥，这样你才能知道哪里出了问题..

Answer 2

我会选择这个：

UPDATE o
SET notes = 'whatever'
FROM orders o
WHERE o.ORDER_DATE >= '20150630 00:00:00' 
  AND o.Email > ' '
  AND o.ORDER_NUMBER IN 
      ( SELECT ol.ORDER_NUMBER 
        FROM Order_Lines ol 
        WHERE ol.PRODUCT_CODE LIKE '15CONF%%'
      )

如果您有很多订单，我会添加一个索引：

create index order_date on orders(order_date) 
  include ( order_number)
  where email > ' ';

fiddle

SQL 更新代码 'Where exisits' 未按预期运行

SQL update code with 'Where exisits' not acting as expected

sql

sql-server

exists