Question

我有一个基于两个表的查询，它们之间有一个导航属性：

// idOrder shared between classes as nav property
public partial class OrderItem
{
    public int idOrder { get; set; }
    public int idInventory { get; set; }
    public virtual Order Order { get; set; }
}

public partial class Order
{           
    public Nullable<short> idSite { get; set; }
    public int idOrder { get; set; }            
    public Nullable<System.DateTime> genDate { get; set; }
    public virtual ICollection<OrderItem> OrderItems { get; set; }
}

当我对它们运行查询时，它似乎与预期的内部联接一起正常工作：

var orderItems = dbc.orderItems
                 .Where(oi => oi.Order.genDate > lastWeek)
                 .Select(oi => oi.idInventory);

返回内部联接查询

SELECT 
[Extent1].[idInventory] AS [idInventory]
FROM  [dbo].[Order_ITEMS] AS [Extent1]
INNER JOIN [dbo].[Order] AS [Extent2] ON [Extent1].[idOrder] = [Extent2].[idOrder]
WHERE [Extent2].[genDate] > @p__linq__0

但是，如果我改为运行非常相似的查询

var orderItems = dbc.orderItems
                 .Where(oi => oi.Order.idSite == 1234)
                 .Select(oi => oi.idInventory);

相反，我得到了这个极其昂贵的外连接查询：

SELECT 
[Extent1].[idInventory] AS [idInventory]
FROM  [dbo].[Order_ITEMS] AS [Extent1]
LEFT OUTER JOIN [dbo].[Order] AS [Extent2] ON [Extent1].[idOrder] = [Extent2].[idOrder]
WHERE  CAST( [Extent2].[idSite] AS int) = @p__linq__0

我相信这是因为idSite是可以为空的，但在这种情况下我并不是要求返回空站点，所以外连接在这里似乎没用。为什么此更改会导致查询更改其连接类型，以及如何阻止它？

为什么整数比较会更改我的查询的连接类型？

0 个答案: