当子记录不存在时，为什么Entity Framework（带有RIA Services）不包括父记录？

Question

Entity Framework 4 is excluding records that I don't believe it should be. Here is my scenario:

Table Definitions

Table_1

    UniqueIdentifier ID not null
    int AnotherField

Table_2

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

There is a relationship between table 1 and table 2 through the table_1ID field. It's defined in the database and the entity framework recognizes it.

I have a Query defined in my DomainService as:

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

If I have a record in table 1 and table 2 that are related, they get returned as expected. If I do NOT have a record in table 2 that relates back to table 1, then the record is getting excluded.

Upon running SQL Server Profiler, I noticed that the entity framework added the following CAST and where clauses:

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

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

So essentially, if the Priority field in Table_2 is null (which it is when there isn't a record in Table 2 that corresponds to the parent Tabe_1 table) the where clause causes both records to drop out (null > 0 fails).

Now, if I change the definition of the Priority field so that it is not required, it eliminates the cast and the check and all is well. But it doesn't seem like I should have to do this.

Have I done something wrong? Is my understanding faulty?

The full EntityQuery and generated query text is below in case it is helpful.

    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'

Table Definition

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

If your foreign key is non null able, then your relation is one to many according to EF, some every child must have parent. So theoretically you can not have child without parent.

If you want to have child without parent, then your relation is zero or one to many, and your foreign key should be null able.

Answer 2

What I've seen of Entity Framework a single Include is always translated as an outer join. With multiple Includes, however, the order of the includes determines whether the joins are inner or outer.

In your example I assume that "Place" is outer joined, whereas both "EventInvitees" and "User" are inner joined. (At least that's what happens when I do a similar query).

If you would change the order into

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

"Place" would be inner joined and "EventInvitees" outer joined (again, based on my similar case).

I cannot find any documentation on the exact logic of this at MSDN, so your result may differ from mine.