當子記錄不存在時，為什么Entity Framework（帶有RIA Services）不包括父記錄？

Question

實體框架4排除了我認為不應該的記錄。 這是我的情況：

表定義

Table_1

    UniqueIdentifier ID not null
    int AnotherField

Table_2

    UniqueIdentifier ID not null
    UniqueIdentifier Table_1ID not null
    int Priority not null

通過table_1ID字段在表1和表2之間存在關系。 它在數據庫中定義，並且實體框架可以識別它。

我在DomainService中定義的查詢為：

private ObjectQuery<Table_1> Table_1WithIncludes()    
{        
    return this.ObjectContext.Table_1        
        .Include("Table_2")                
}

如果我在表1和表2中有相關記錄，它們將按預期返回。 如果我在表2中沒有與表1相關的記錄，那么該記錄將被排除在外。

運行SQL Server Profiler后，我注意到實體框架添加了以下CAST和where子句：

CASE WHEN ([Join2].[Priority] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]

WHERE ([Project1].[C1] > 0) 

因此，從本質上講，如果Table_2中的Priority字段為null（當表2中沒有與父Tabe_1表相對應的記錄時就是這種情況），where子句會導致兩條記錄都丟失（null> 0失敗）。

現在，如果我更改“優先級”字段的定義，使它不是必需的，則它消除了強制類型轉換和檢查，一切都很好。 但這似乎不應該我要做。

我做錯什么了嗎？ 我的理解有誤嗎？

如果有幫助，請在下面查看完整的EntityQuery和生成的查詢文本。

    private ObjectQuery<Event> EventsWithIncludes()
    {
        return this.ObjectContext.Events
            .Include("Place")
            .Include("EventInvitees")
            .Include("EventInvitees.User");
    }


exec sp_executesql N'SELECT 
[Project2].[NumberOfPeople] AS [NumberOfPeople], 
[Project2].[ID] AS [ID], 
[Project2].[CreatorID] AS [CreatorID], 
[Project2].[CreateDate] AS [CreateDate], 
[Project2].[PlacesID] AS [PlacesID], 
[Project2].[EventDate] AS [EventDate], 
[Project2].[EventTime] AS [EventTime], 
[Project2].[Availability] AS [Availability], 
[Project2].[EscalationLevels] AS [EscalationLevels], 
[Project2].[Rank] AS [Rank], 
[Project2].[RowVersion] AS [RowVersion], 
[Project2].[ID1] AS [ID1], 
[Project2].[Name] AS [Name], 
[Project2].[Phone] AS [Phone], 
[Project2].[DefaultPar] AS [DefaultPar], 
[Project2].[DefaultSlope] AS [DefaultSlope], 
[Project2].[DefaultRating] AS [DefaultRating], 
[Project2].[CreateDate1] AS [CreateDate1], 
[Project2].[UpdateDate] AS [UpdateDate], 
[Project2].[MetroAreaID] AS [MetroAreaID], 
[Project2].[C1] AS [C1], 
[Project2].[PriorityOrder] AS [PriorityOrder], 
[Project2].[ID2] AS [ID2], 
[Project2].[EventsID] AS [EventsID], 
[Project2].[InviteeUsersID] AS [InviteeUsersID], 
[Project2].[RowVersion1] AS [RowVersion1], 
[Project2].[Attending] AS [Attending], 
[Project2].[StatusChange] AS [StatusChange], 
[Project2].[ID3] AS [ID3], 
[Project2].[First] AS [First], 
[Project2].[Last] AS [Last], 
[Project2].[UserName] AS [UserName], 
[Project2].[Password] AS [Password], 
[Project2].[Gender] AS [Gender], 
[Project2].[Email] AS [Email], 
[Project2].[Email_Sharing] AS [Email_Sharing], 
[Project2].[Email_Receive] AS [Email_Receive], 
[Project2].[Phone1] AS [Phone1], 
[Project2].[Phone_Sharing] AS [Phone_Sharing], 
[Project2].[Phone_Receive] AS [Phone_Receive], 
[Project2].[CreateDate2] AS [CreateDate2], 
[Project2].[UpdateDate1] AS [UpdateDate1]
FROM ( SELECT 
    [Project1].[ID] AS [ID], 
    [Project1].[CreatorID] AS [CreatorID], 
    [Project1].[CreateDate] AS [CreateDate], 
    [Project1].[NumberOfPeople] AS [NumberOfPeople], 
    [Project1].[PlacesID] AS [PlacesID], 
    [Project1].[EventDate] AS [EventDate], 
    [Project1].[Availability] AS [Availability], 
    [Project1].[EscalationLevels] AS [EscalationLevels], 
    [Project1].[Rank] AS [Rank], 
    [Project1].[RowVersion] AS [RowVersion], 
    [Project1].[EventTime] AS [EventTime], 
    [Extent3].[ID] AS [ID1], 
    [Extent3].[Name] AS [Name], 
    [Extent3].[Phone] AS [Phone], 
    [Extent3].[DefaultPar] AS [DefaultPar], 
    [Extent3].[DefaultSlope] AS [DefaultSlope], 
    [Extent3].[DefaultRating] AS [DefaultRating], 
    [Extent3].[CreateDate] AS [CreateDate1], 
    [Extent3].[UpdateDate] AS [UpdateDate], 
    [Extent3].[MetroAreaID] AS [MetroAreaID], 
    [Join2].[ID1] AS [ID2], 
    [Join2].[EventsID] AS [EventsID], 
    [Join2].[InviteeUsersID] AS [InviteeUsersID], 
    [Join2].[PriorityOrder] AS [PriorityOrder], 
    [Join2].[RowVersion] AS [RowVersion1], 
    [Join2].[Attending] AS [Attending], 
    [Join2].[StatusChange] AS [StatusChange], 
    [Join2].[ID2] AS [ID3], 
    [Join2].[First] AS [First], 
    [Join2].[Last] AS [Last], 
    [Join2].[UserName] AS [UserName], 
    [Join2].[Password] AS [Password], 
    [Join2].[Gender] AS [Gender], 
    [Join2].[Email] AS [Email], 
    [Join2].[Email_Sharing] AS [Email_Sharing], 
    [Join2].[Email_Receive] AS [Email_Receive], 
    [Join2].[Phone] AS [Phone1], 
    [Join2].[Phone_Sharing] AS [Phone_Sharing], 
    [Join2].[Phone_Receive] AS [Phone_Receive], 
    [Join2].[CreateDate] AS [CreateDate2], 
    [Join2].[UpdateDate] AS [UpdateDate1], 
    CASE WHEN ([Join2].[PriorityOrder] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
    FROM    (SELECT 
        [Extent1].[ID] AS [ID], 
        [Extent1].[CreatorID] AS [CreatorID], 
        [Extent1].[CreateDate] AS [CreateDate], 
        [Extent1].[NumberOfPeople] AS [NumberOfPeople], 
        [Extent1].[PlacesID] AS [PlacesID], 
        [Extent1].[EventDate] AS [EventDate], 
        [Extent1].[Availability] AS [Availability], 
        [Extent1].[EscalationLevels] AS [EscalationLevels], 
        [Extent1].[Rank] AS [Rank], 
    [Extent1].[RowVersion] AS [RowVersion], 
    [Extent1].[EventTime] AS [EventTime], 
    (SELECT 
        COUNT(1) AS [A1]
        FROM [dbo].[EventInvitees] AS [Extent2]
        WHERE ([Extent1].[ID] = [Extent2].[EventsID]) AND ([Extent2].[InviteeUsersID] = @p__linq__2)) AS [C1]
    FROM [dbo].[Events] AS [Extent1] ) AS [Project1]
LEFT OUTER JOIN [dbo].[Places] AS [Extent3] ON [Project1].[PlacesID] = [Extent3].[ID]
LEFT OUTER JOIN  (SELECT [Extent4].[ID] AS [ID1], [Extent4].[EventsID] AS [EventsID], [Extent4].[InviteeUsersID] AS [InviteeUsersID], [Extent4].[PriorityOrder] AS [PriorityOrder], [Extent4].[RowVersion] AS [RowVersion], [Extent4].[Attending] AS [Attending], [Extent4].[StatusChange] AS [StatusChange], [Extent5].[ID] AS [ID2], [Extent5].[First] AS [First], [Extent5].[Last] AS [Last], [Extent5].[UserName] AS [UserName], [Extent5].[Password] AS [Password], [Extent5].[Gender] AS [Gender], [Extent5].[Email] AS [Email], [Extent5].[Email_Sharing] AS [Email_Sharing], [Extent5].[Email_Receive] AS [Email_Receive], [Extent5].[Phone] AS [Phone], [Extent5].[Phone_Sharing] AS [Phone_Sharing], [Extent5].[Phone_Receive] AS [Phone_Receive], [Extent5].[CreateDate] AS [CreateDate], [Extent5].[UpdateDate] AS [UpdateDate]
    FROM  [dbo].[EventInvitees] AS [Extent4]
    INNER JOIN [dbo].[Users] AS [Extent5] ON [Extent4].[InviteeUsersID] = [Extent5].[ID] ) AS [Join2] ON [Project1].[ID] = [Join2].[EventsID]
WHERE ([Project1].[C1] > 0) AND ([Project1].[CreatorID] = @p__linq__0) AND (([Project1].[EventDate] IS NULL) OR ([Project1].[EventDate] >= @p__linq__1))
)  AS [Project2]
ORDER BY [Project2].[ID] ASC, [Project2].[ID1] ASC, [Project2].[C1] ASC',N'@p__linq__2     uniqueidentifier,@p__linq__0 uniqueidentifier,@p__linq__1 datetime2(7)',@p__linq__2='33BB8199-7B25-4B3A-B96D-044EB7DB70AE',@p__linq__0='33BB8199-7B25-4B3A-B96D-044EB7DB70AE',@p__linq__1='1900-01-01 00:00:00'

表定義

USE [TheGreen18]
GO

/****** Object:  Table [dbo].[EventInvitees]    Script Date: 03/17/2012 22:27:16 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

CREATE TABLE [dbo].[EventInvitees](
    [ID] [uniqueidentifier] NOT NULL,
    [EventsID] [uniqueidentifier] NOT NULL,
    [InviteeUsersID] [uniqueidentifier] NOT NULL,
    [PriorityOrder] [int] NOT NULL,
    [RowVersion] [timestamp] NULL,
    [Attending] [bit] NULL,
    [StatusChange] [datetime] NULL,
 CONSTRAINT [PK_EventInvitees] PRIMARY KEY CLUSTERED 
(
    [ID] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[EventInvitees]  WITH CHECK ADD  CONSTRAINT [FK_EventInvitees_Events] FOREIGN KEY([EventsID])
REFERENCES [dbo].[Events] ([ID])
ON DELETE CASCADE
GO

ALTER TABLE [dbo].[EventInvitees] CHECK CONSTRAINT [FK_EventInvitees_Events]
GO

ALTER TABLE [dbo].[EventInvitees]  WITH CHECK ADD  CONSTRAINT [FK_EventInvitees_Users] FOREIGN KEY([InviteeUsersID])
REFERENCES [dbo].[Users] ([ID])
GO

ALTER TABLE [dbo].[EventInvitees] CHECK CONSTRAINT [FK_EventInvitees_Users]
GO

Answer 1

如果您的外鍵不能為空，那么根據EF，您的關系是一對多的，每個孩子必須有父母。 因此，從理論上講，沒有父母就不能有孩子。

如果您想生一個沒有父母的孩子，那么您的關系為零或一對多，並且您的外鍵應該為空。

Answer 2

我對實體框架所見的單個“ Include始終被翻譯為外部聯接。 但是，對於多個包含，包含的順序確定連接是內部連接還是外部連接。

在您的示例中，我假定“地方”是外部聯接的，而“ EventInvitees”和“用戶”都是內部聯接的。 （至少當我執行類似的查詢時，會發生這種情況）。

如果您將訂單更改為

.Include("EventInvitees")
.Include("EventInvitees.User")
.Include("Place")

“地方”將內部連接，“事件邀請”外部將連接（同樣，基於我的類似案例）。

我在MSDN上找不到任何有關此邏輯的文檔，因此您的結果可能與我的不同。