3

我的一个项目的配置遇到问题，并且生成的 SQL EF 似乎显示出一些意想不到的（至少对我而言）嵌套。这个问题会有点啰嗦，但请多多包涵。

所以，假设我有以下设置：

public class Order
{
    public int Id { get; set; }
    public decimal Amount { get; set; }
    public Address ShippingAddress { get; set; }
}

public class Person
{
    public int Id { get; set; }
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public Address Address { get; set; }
}

public class Address
{
    public int Id { get; set; }
    public string StreetAddress { get; set; }
    public string City { get; set; }
    public string State { get; set; }
    public string ZipCode { get; set; }
}

实体配置如下：

public class OrderConfiguration : EntityTypeConfiguration<Order>
{
    public OrderConfiguration()
    {
        ToTable("Orders");

        HasRequired(order => order.ShippingAddress)
            .WithRequiredDependent()
            .Map(mapping => mapping.MapKey("ShippingAddressId"));
    }
}

public class PersonConfiguration : EntityTypeConfiguration<Person>
{
    public PersonConfiguration()
    {
        ToTable("Persons");

        HasRequired(person => person.Address)
            .WithRequiredDependent()
            .Map(mapping => mapping.MapKey("AddressId"));
    }
}

我的目标是获取包含地址的订单，因此我运行了一个简单的查询，例如：

var orders = context.Orders
    .Include(order => order.ShippingAddress)
    .Where(order => order.ShippingAddress.State == "FL")
    .ToList();

当我监视 SQL Profiler 时，我希望看到生成的 SQL 从 Orders 表中选择并在 Address 表上进行内部连接

 SELECT * FROM [dbo].[Orders] AS [Extent1] 
     INNER JOIN [dbo].[Addresses] AS [Extent2] ON [Extent1].[AddressId] = [Extentd2].[Id]
     WHERE [Extent2].[State] == 'FL'

相反，我发现这是生成的：

SELECT 
[Extent1].[Id] AS [Id], 
[Extent1].[Amount] AS [Amount], 
[Join5].[Id1] AS [Id1], 
[Join5].[StreetAddress] AS [StreetAddress], 
[Join5].[City] AS [City], 
[Join5].[State] AS [State], 
[Join5].[ZipCode] AS [ZipCode], 
[Join8].[Id2] AS [Id2], 
[Join11].[Id3] AS [Id3]
FROM     [dbo].[Orders] AS [Extent1]
INNER JOIN  (SELECT [Extent2].[State] AS [State], [Extent3].[Id] AS [Id4]
    FROM   [dbo].[Addresses] AS [Extent2]
    LEFT OUTER JOIN [dbo].[Orders] AS [Extent3] ON [Extent2].[Id] = [Extent3].[ShippingAddressId]
    LEFT OUTER JOIN [dbo].[Persons] AS [Extent4] ON [Extent2].[Id] = [Extent4].[AddressId] ) AS [Join2] ON [Extent1].[Id] = [Join2].[Id4]
LEFT OUTER JOIN  (SELECT [Extent5].[Id] AS [Id1], [Extent5].[StreetAddress] AS [StreetAddress], [Extent5].[City] AS [City], [Extent5].[State] AS [State], [Extent5].[ZipCode] AS [ZipCode], [Extent6].[Id] AS [Id5]
    FROM   [dbo].[Addresses] AS [Extent5]
    LEFT OUTER JOIN [dbo].[Orders] AS [Extent6] ON [Extent5].[Id] = [Extent6].[ShippingAddressId]
    LEFT OUTER JOIN [dbo].[Persons] AS [Extent7] ON [Extent5].[Id] = [Extent7].[AddressId] ) AS [Join5] ON [Extent1].[Id] = [Join5].[Id5]
LEFT OUTER JOIN  (SELECT [Extent9].[Id] AS [Id2]
    FROM   [dbo].[Addresses] AS [Extent8]
    LEFT OUTER JOIN [dbo].[Orders] AS [Extent9] ON [Extent8].[Id] = [Extent9].[ShippingAddressId]
    LEFT OUTER JOIN [dbo].[Persons] AS [Extent10] ON [Extent8].[Id] = [Extent10].[AddressId] ) AS [Join8] ON [Extent1].[Id] = [Join8].[Id2]
LEFT OUTER JOIN  (SELECT [Extent12].[Id] AS [Id6], [Extent13].[Id] AS [Id3]
    FROM   [dbo].[Addresses] AS [Extent11]
    LEFT OUTER JOIN [dbo].[Orders] AS [Extent12] ON [Extent11].[Id] = [Extent12].[ShippingAddressId]
    LEFT OUTER JOIN [dbo].[Persons] AS [Extent13] ON [Extent11].[Id] = [Extent13].[AddressId] ) AS [Join11] ON [Extent1].[Id] = [Join11].[Id6]
WHERE N'FL' = [Join2].[State]

显然，这比需要做的工作多得多。有没有更简单的方法可以做到这一点，还是我的实体配置不正确？我不明白为什么它要撤回所有这些额外的连接，或者我如何才能将它们限制在我当时需要的表中。任何见解将不胜感激！

谢谢，德里克

4

1 回答 1

1

正如您所注意到的.Include()，有时会生成可怕的 SQL！

我发现在这种情况下最简单的解决方案是在初始加载后直接显式加载所需的相关实体。这样做的缺点是额外的数据库调用 - 每个订单都会调用一次。

var orders = (
    from order in context.Orders
    where order.ShippingAddress.State == "FL"
    select order)
    .ToList();

var t1 = (
    from order in orders
    from address in order.ShippingAddress
    select address)
    .ToList();
于 2013-03-11T15:30:11.477 回答