Question

我编写了一个触发器，用于从OrderDetails状态更新为Order状态：

BEGIN
    /* 
        Order Status:
            Pending = 0,
            Processing = 1,
            Proceeded = 2,
            Completed = 3,
            Cancelled = 4,
        Order Detail Status:
            Pending = 0,
            Processing = 1,
            Proceeded = 2,
            Emailed = 3,
            Ordered = 4,
            Cancelled = 5
    */
    IF (UPDATE([Status]))
    BEGIN   
        UPDATE [Order]
        SET [Status] = 
            CASE (SELECT MIN(od.[Status]) FROM OrderDetail od WHERE od.OrderId = i.OrderId)
                WHEN 5 THEN 4
                WHEN 4 THEN 3
                WHEN 3 THEN 2
                WHEN 2 THEN 2
                WHEN 1 THEN 1
                WHEN 0 THEN 0
            END
        FROM INSERTED i
        WHERE [Order].Id = i.OrderId
    END
END

您可以看到，当OrderDetailStatus = 2或3时，OrderStatus = 2，否则OrderStatus = OrderDetailStatus。现在，我必须列出状态值。因此，是否可以为value语句创建别名，如下所示：

SET [Status] = 
            CASE (SELECT MIN(od.[Status]) FROM OrderDetail od WHERE od.OrderId = i.OrderId) AS val
                WHEN 3 THEN 2
                ELSE val
            END
        FROM INSERTED i
        WHERE [Order].Id = i.OrderId

Answer 1

我想“缩短”的唯一方法是：

UPDATE O
SET [Status] = CASE WHEN od.[Status] BETWEEN 3 AND 5 THEN od.[Status] - 1 ELSE od.[Status] END
FROM [Order] O
     JOIN INSERTED i ON O.Id = i.OrderId
     CROSS APPLY (SELECT MIN(od.[Status]) AS [Status]
                  FROM OrderDetail ca
                  WHERE ca.OrderId = i.OrderId) od;

换句话说，您应该真正避免使用保留（甚至键）字作为对象名。 ORDER是SQL Server中的保留字，因此实际上不应该使用。 Status是一个关键字，可以这样，但也应避免。

别名，以防sqlserver

1 个答案: