Question

我是一名EF新手，所以请耐心等待：o

我的数据库中有一个非常直接的关系。 ts_Order表{ID，OrderDate，OrderNumber}和ts_OrderDetails表{ID，ProductId，OrderID}。两个表中的ID都是PK和Identity列。 ts_OrderDetails表中的OrderID是FK，并引用ts_Order表的ID列。

我需要选择所有订单以及每个订单可能包含的每个细节。在SQL中我会写这样的东西：

select * from ts_Order ORD inner join ts_OrderDetails DTL on ORD.ID=DTL.OrderID

哪种效果很好。

当我尝试在EF中做类似的事情时：

List<Order> result = context.Orders.Include("OrderDetails").Where(i => i.ID > 0).ToList();

这是由EF生成的：

SELECT 
[Project1].[ID] AS [ID], 
[Project1].[OrderDate] AS [OrderDate], 
[Project1].[OrderNumber] AS [OrderNumber], 
[Project1].[C1] AS [C1], 
[Project1].[ID1] AS [ID1], 
[Project1].[Product] AS [Product], 
[Project1].[OrderID] AS [OrderID]
FROM ( SELECT 
    [Extent1].[ID] AS [ID], 
    [Extent1].[OrderDate] AS [OrderDate], 
    [Extent1].[OrderNumber] AS [OrderNumber], 
    [Extent2].[ID] AS [ID1], 
    [Extent2].[Product] AS [Product], 
    [Extent2].[OrderID] AS [OrderID], 
    CASE WHEN ([Extent2].[ID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
    FROM  [dbo].[ts_Order] AS [Extent1]
    LEFT OUTER JOIN (SELECT 
      [ts_OrderDetails].[ID] AS [ID], 
      [ts_OrderDetails].[Product] AS [Product], 
      [ts_OrderDetails].[OrderID] AS [OrderID]
      FROM [dbo].[ts_OrderDetails] AS [ts_OrderDetails]) AS [Extent2] ON [Extent1].[ID] = [Extent2].[OrderID]
    WHERE [Extent1].[ID] > 0
)  AS [Project1]
ORDER BY [Project1].[ID] ASC, [Project1].[C1] ASC

为什么生成的查询如此复杂？我错过了什么吗？

-Vinod

Answer 1

根据我看到的EF生成的一些东西实际上并不是太糟糕。你没有做错任何事。

如果您想获得有关EF用于生成结果的过程的更多信息，这是一个很好的阅读。也是一个很好的指导，使EF尽可能高效。

http://msdn.microsoft.com/en-us/library/cc853327.aspx

EF - 生成的一对多选择查询中的问题

1 个答案: