初学sql问题pt.2错误ora-00933 SQL命令没有正确结束

Question

我必须更新我的表，以便在DBMS中完成我的任务。无法弄清楚为什么我得到这个错误。

UPDATE Customers 
    SET CreditLimit = CreditLimit * 1.25 
     FROM(SELECT * 
      FROM Orders 
      WHERE Amount > 250 
      HAVING COUNT(*) >= 2); 

任何想法？

Answer 1

的update声明没有一个from条款，如您指定。
您是否想要做这样的事情： 对于至少有2个订单超过250个货币的客户，将信用额度增加25％。

update Customers 
    set CreditLimit = CreditLimit * 1.25 
where (select count(*) 
      from Orders 
     where Amount > 250 
      and orders.customer_id = Customers.customer_id)) >= 2; 

编辑
我刚才注意到您使用的是Oracle（ORA的消息）。由于您有可能更新所有客户，我相信最高性能的方式是使用“可更新连接”或下面的合并语句：

merge 
into customers 
using (select customer_id 
     from Orders o 
     where amount > 250 
     group 
      by customer_id 
     having count(*) >= 2 
    ) orders 
    on(customers.customer_id = orders.customer_id) 
when matched then 
    update 
     set customers.creditlimit = customers.creditlimit * 1.25; 

Answer 2

UPDATE Customers 
     SET CreditLimit = CreditLimit * 1.25 
      FROM Customers 
    Where Id in (
    select CustomerId 
    from orders 
    where Amount > 250 
    Group By CustomerId 
    HAVING COUNT(*) >= 2); 

或

UPDATE Customers 
     SET CreditLimit = CreditLimit * 1.25 
      FROM Customers c 
    Where (select count(*) from orders o where o.CustomerId = c.Id And Amount > 250) > =2