Question

背景

我有2个表：OrderItem和OrderItemValue。 OrderItem可以有0或1个OrderItemPackageValue。两个表中的主键是相同的，并且有一个从OrderItems到OrderItemPackageValue的外键引用

LINQ

var dummy = 
    from orderItem in context.OrderItems
    select new 
    {
        OrderID = orderItem.OrderID,
        LineNumber = orderItem.LineNumber,
        PackageValue = (decimal?)orderItem.OrderItemPackageValue.PackageValue
    };

var dummy2 = dummy.ToArray();

SQL

   SELECT 
   [Extent1].[OrderID] AS [OrderID], 
   [Extent1].[LineNumber] AS [LineNumber], 
   [Extent3].[PackageValue] AS [PackageValue]
   FROM   [dbo].[OrderItems] AS [Extent1]
   LEFT OUTER JOIN [dbo].[OrderItemPackageValues] AS [Extent2] ON ([Extent1].[OrderID] =   [Extent2].[OrderID]) AND ([Extent1].[LineNumber] = [Extent2].[LineNumber])
   LEFT OUTER JOIN [dbo].[OrderItemPackageValues] AS [Extent3] ON ([Extent2].[OrderID] = [Extent3].[OrderID]) AND ([Extent2].[LineNumber] = [Extent3].[LineNumber])

我试图通过Linq2Entities（MSSQL）获得这个，它似乎正在生成一个额外的外连接，我无法弄清楚如何摆脱它。

Answer 1

这是一个错误;请参阅here和here。

解决方法：尝试将您的关系从1 : Many更改为0..1 : Many

为什么LINQ-to-Entities正在生成额外的左外连接

1 个答案: