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

Question

实体框架4排除了我认为不应该的记录。 这是我的情况：

表定义

Table_1

    UniqueIdentifier ID not null
    int AnotherField

Table_2

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

通过table_1ID字段在表1和表2之间存在关系。 它在数据库中定义，并且实体框架可以识别它。

我在DomainService中定义的查询为：

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

如果我在表1和表2中有相关记录，它们将按预期返回。 如果我在表2中没有与表1相关的记录，那么该记录将被排除在外。

运行SQL Server Profiler后，我注意到实体框架添加了以下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，从本质上讲，如果Table_2中的Priority字段为null（当表2中没有与父Tabe_1表相对应的记录时就是这种情况），where子句会导致两条记录都丢失（null> 0失败）。

现在，如果我更改“优先级”字段的定义，使它不是必需的，则它消除了强制类型转换和检查，一切都很好。 但这似乎不应该我要做。

我做错什么了吗？ 我的理解有误吗？

如果有帮助，请在下面查看完整的EntityQuery和生成的查询文本。

    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'

表定义

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

如果您的外键不能为空，那么根据EF，您的关系是一对多的，每个孩子必须有父母。 因此，从理论上讲，没有父母就不能有孩子。

如果您想生一个没有父母的孩子，那么您的关系为零或一对多，并且您的外键应该为空。

Answer 2

我对实体框架所见的单个“ Include始终被翻译为外部联接。 但是，对于多个包含，包含的顺序确定连接是内部连接还是外部连接。

在您的示例中，我假定“地方”是外部联接的，而“ EventInvitees”和“用户”都是内部联接的。 （至少当我执行类似的查询时，会发生这种情况）。

如果您将订单更改为

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

“地方”将内部连接，“事件邀请”外部将连接（同样，基于我的类似案例）。

我在MSDN上找不到任何有关此逻辑的文档，因此您的结果可能与我的不同。