我使用EntityFramework 4 +生成的POCO,延迟加载禁用。
假设有一些名为 Table1,Table2,Table3 和 Table4 的SQL表,并假设它们包含一些数据。
让我们假设这些表的简化POCO表示如下:
public class Table1
{
public int ID;
public DateTime TableDate;
public int Table2ID;
public Table2 Table2;
public ICollection<Table3> Table3s;
}
public class Table2
{
public int ID;
public string SomeString;
public int Table4ID;
public Table4 Table4;
}
public class Table3
{
public int ID;
public int Table1ID;
public Table1 Table1;
public decimal SomeDecimal;
}
public decimal Table4
{
public int ID;
public string SomeName;
}
如果执行以下代码:
Database DB = new Database(); // object context
var result = DB.Table1
.Where(x => x.TableDate >= DateTime.MinValue);
EF将生成以下SQL语句:
exec sp_executesql N'SELECT
[Extent1].[ID] AS [ID],
[Extent1].[TableDate] AS [TableDate],
[Extent1].[Table2ID] As [Table2ID]
FROM [dbo].[Table1] AS [Extent1]
WHERE ([Extent1].[TableDate] >= @p__linq__0)',N'@p__linq__0 datetime2(7)',@p__linq__0='0001-01-01 00:00:00'
并且查询将返回预期的数据 但是,如果执行以下代码:
Database DB = new Database(); // object context
var result = DB.Table1
.Include("Table2")
.Include("Table2.Table4")
.Include("Table3")
.Where(x => x.TableDate >= DateTime.MinValue);
EF将生成以下SQL语句:
exec sp_executesql N'SELECT
[Project1].[ID2] AS [ID],
[Project1].[ID] AS [ID1],
[Project1].[TableDate] AS [TableDate],
[Project1].[ID1] AS [ID2],
[Project1].[SomeString] AS [SomeString],
[Project1].[Table4ID] AS [Table4ID],
[Project1].[ID3] AS [ID3],
[Project1].[SomeName] AS [SomeName],
[Project1].[ID4] AS [ID4],
[Project1].[SomeDecimal] AS [SomeDecimal],
[Project1].[Table1ID] AS [Table1ID]
FROM ( SELECT
[Extent1].[ID] AS [ID],
[Extent1].[TableDate] AS [TableDate],
[Extent2].[ID] AS [ID1],
[Extent2].[SomeString] AS [SomeString],
[Extent2].[Table4ID] AS [Table4ID],
[Extent3].[ID] AS [ID2],
[Extent4].[ID] AS [ID3],
[Extent4].[SomeName] AS [SomeName],
[Extent5].[ID] AS [ID4],
[Extent5].[SomeDecimal] AS [SomeDecimal],
[Extent5].[Table1ID] AS [Table1ID],
CASE WHEN ([Extent5].[ID] IS NULL) THEN CAST(NULL AS int) ELSE 1 END AS [C1]
FROM [dbo].[Table1] AS [Extent1]
INNER JOIN [dbo].[Table2] AS [Extent2] ON [Extent1].[Table2ID] = [Extent2].[ID]
LEFT OUTER JOIN [dbo].[Table2] AS [Extent3] ON [Extent1].[Table2ID] = [Extent3].[ID]
LEFT OUTER JOIN [dbo].[Table4] AS [Extent4] ON [Extent3].[Table4ID] = [Extent4].[ID]
LEFT OUTER JOIN [dbo].[Table3] AS [Extent5] ON [Extent1].[ID] = [Extent5].[Table1ID]
WHERE ([Extent1].[TableDate] >= @p__linq__0)
) AS [Project1]
ORDER BY [Project1].[ID2] ASC, [Project1].[ID] ASC, [Project1].[ID1] ASC, [Project1].[ID3] ASC, [Project1].[C1] ASC',N'@p__linq__0 datetime2(7)',@p__linq__0='0001-01-01 00:00:00'
并且查询将不返回任何内容。
为什么会发生这种情况?
修改的
以下是用于创建上述表的SQL语句:
CREATE TABLE [dbo].[Table1](
[ID] [int] IDENTITY(1,1) NOT NULL,
[Table2ID] [int] NOT NULL,
[TableDate] [date] NOT NULL,
CONSTRAINT [PK_Table1] 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]
ALTER TABLE [dbo].[Table1] WITH NOCHECK ADD CONSTRAINT [FK_Table1_Table2] FOREIGN KEY([Table2ID])
REFERENCES [dbo].[Table2] ([ID])
ALTER TABLE [dbo].[Table1] CHECK CONSTRAINT [FK_Table1_Table2]
CREATE TABLE [dbo].[Table2](
[ID] [int] NOT NULL,
[SomeString] [nvarchar](50) NOT NULL,
[Table4ID] [int] NULL,
CONSTRAINT [PK_Table2] 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]
ALTER TABLE [dbo].[Table2] WITH NOCHECK ADD CONSTRAINT [FK_Table2_Table4] FOREIGN KEY([Table4ID])
REFERENCES [dbo].[Table4] ([ID])
ON UPDATE CASCADE
ALTER TABLE [dbo].[Table2] CHECK CONSTRAINT [FK_Table2_Table4]
CREATE TABLE [dbo].[Table3](
[ID] [int] IDENTITY(1,1) NOT NULL,
[SomeDecimal] [decimal](18, 4) NOT NULL,
[Table1ID] [int] NOT NULL,
CONSTRAINT [PK_Table3] 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]
ALTER TABLE [dbo].[Table3] WITH NOCHECK ADD CONSTRAINT [FK_Table3_Table1] FOREIGN KEY([Table1ID])
REFERENCES [dbo].[Table1] ([ID])
ON DELETE CASCADE
ALTER TABLE [dbo].[Table3] CHECK CONSTRAINT [FK_Table3_Table1]
CREATE TABLE [dbo].[Table4](
[ID] [int] NOT NULL,
[SomeName] [nvarchar](50) NOT NULL,
CONSTRAINT [PK_Table4] 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]
编辑2
此查询也不会返回任何记录,可以作为最小示例:
Database DB = new Database();
var result = DB.Table1
.Include("Table2")
.Where(x => x.TableDate >= DateTime.MinValue);
生成的SQL:
exec sp_executesql N'SELECT
[Extent1].[ID] AS [ID],
[Extent1].[Table2ID] AS [Table2ID],
[Extent1].[TableDate] AS [TableDate],
[Extent2].[ID] AS [ID1],
[Extent2].[SomeString] AS [SomeString],
[Extent2].[Table4ID] AS [Table4ID],
FROM [dbo].[Table1] AS [Extent1]
INNER JOIN [dbo].[Table2] AS [Extent2] ON [Extent1].[Table2ID] = [Extent2].[ID]
WHERE ([Extent1].[TableDate] >= @p__linq__0)',N'@p__linq__0 datetime2(7)',@p__linq__0='0001-01-01 00:00:00'
此外,这里摘录自.edmx:
<EntityContainer>
<AssociationSet Name="FK_Table1_Table2" Association="MyModel.Store.FK_Table1_Table2">
<End Role="Table2" EntitySet="Table2" />
<End Role="Table1" EntitySet="Table1" />
</AssociationSet>
</EntityContainer>
<!-- ... -->
<EntityType Name="Table2">
<Key>
<PropertyRef Name="ID" />
</Key>
<Property Name="ID" Type="int" Nullable="false" />
<Property Name="SomeString" Type="nvarchar" Nullable="false" MaxLength="50" />
<Property Name="Table4ID" Type="int" />
</EntityType>
<!-- ... -->
<EntityType Name="Table1">
<Key>
<PropertyRef Name="ID" />
</Key>
<Property Name="ID" Type="int" Nullable="false" StoreGeneratedPattern="Identity" />
<Property Name="TableDate" Type="date" Nullable="false" />
<Property Name="Table2ID" Type="int" Nullable="false" />
</EntityType>
<!-- ... -->
<Association Name="FK_Table1_Table2">
<End Role="Table2" Type="MyModel.Store.Table2" Multiplicity="1" />
<End Role="Table1" Type="MyModel.Store.Table1" Multiplicity="*" />
<ReferentialConstraint>
<Principal Role="Table2">
<PropertyRef Name="ID" />
</Principal>
<Dependent Role="Table1">
<PropertyRef Name="Table2ID" />
</Dependent>
</ReferentialConstraint>
</Association>
答案 0 :(得分:1)
似乎SQL服务器中的实际数据不一致是个问题 如上所述there,
当两个表中至少有一个匹配项时,INNER JOIN关键字返回行。如果“Table1”中的行中没有“Table2”中的匹配项,则不会列出这些行。
此查询没有理由失败,除非“Table2”中没有与“Table1”匹配的行。这很奇怪,因为FK约束被强制执行,但这值得另一个问题,这个案例已经结束。
答案 1 :(得分:0)
我的猜测是Include()导致您的查询没有按照您期望的顺序进行评估,因此在调用Where()时TableDate不可用。如果你强制评估,然后调用你的Where()怎么办?