优化实体框架的LINQ查询（选择1意外场）

Question

所有，

谁能帮我优化下EF/Linq查询：

的EF/Linq查询（从LinqPad拍摄）：

Articles 
    .AsNoTracking() 
    .Where(a => a.Active == "J") 
    .SelectMany(a => KerlServices 
     .Where(ks => ks.Service.SAPProductNumber == a.SAPProductNumber)) 
    .Select(ks => new { 
     ks.KerlCode, 
     ks.Service.SAPProductNumber, 
     ks.Service.Type }) 
    .ToList() 

文章与服务之间的关系（ks.Service.SAPProductNumber == a.SAPProductNumber）理论上是1：可选关系，不能在EF中定义。但是，这是而不是我的问题。

产生的SQL查询：

SELECT 
    [Join1].[F_SERVICESID] AS [F_SERVICESID], 
    [Join1].[F_KERLCOD] AS [F_KERLCOD], 
    [Join1].[F_SAPARTNUM] AS [F_SAPARTNUM], 
    [Join1].[F_TYPE] AS [F_TYPE] 
    FROM [dbo].[T_ART] AS [Extent1] 
    INNER JOIN (SELECT [Extent2].[F_KERLCOD] AS [F_KERLCOD], [Extent2].[F_SERVICESID] AS [F_SERVICESID], [Extent3].[F_SAPARTNUM] AS [F_SAPARTNUM], [Extent3].[F_TYPE] AS [F_TYPE] 
     FROM [dbo].[T_SERVICESKERL] AS [Extent2] 
     INNER JOIN [dbo].[T_SERVICES] AS [Extent3] ON [Extent2].[F_SERVICESID] = [Extent3].[F_ID]) AS [Join1] ON [Extent1].[F_SAPARTNUM] = [Join1].[F_SAPARTNUM] 
    WHERE N'J' = [Extent1].[F_ACTIND] 

为什么EF产生选择[Join1]查询[F_SERVICESID]？我不需要这个领域。有谁知道一种方法来防止这种情况？

亲切的问候，月

加入1：

KerlServices 
    .AsNoTracking() 
    .Select(ks => new { 
     ks.KerlCode, 
     ks.Service.SAPProductNumber, 
     ks.Service.Type }) 
    .Join(
     Articles, 
     ks => ks.SAPProductNumber, 
     a => a.SAPProductNumber, 
     (ks, a) => new { ks, a.Active }) 
    .Where(ksa => ksa.Active == "J") 
    .Select(ksa => ksa.ks) 
    .ToList() 

结果：

SELECT 
    [Extent1].[F_SERVICESID] AS [F_SERVICESID], 
    [Extent1].[F_KERLCOD] AS [F_KERLCOD], 
    [Extent2].[F_SAPARTNUM] AS [F_SAPARTNUM], 
    [Extent2].[F_TYPE] AS [F_TYPE] 
    FROM [dbo].[T_SERVICESKERL] AS [Extent1] 
    INNER JOIN [dbo].[T_SERVICES] AS [Extent2] ON [Extent1].[F_SERVICESID] = [Extent2].[F_ID] 
    INNER JOIN [dbo].[T_ART] AS [Extent3] ON [Extent2].[F_SAPARTNUM] = [Extent3].[F_SAPARTNUM] 
    WHERE N'J' = [Extent3].[F_ACTIND] 

这种 '改进' 不回答我的问题，但肯定的结果看起来更漂亮。

更新1：

伊万Stoev的答案查询生成的SQL语句：

SELECT 
    [Extent1].[F_SERVICESID] AS [F_SERVICESID], 
    [Extent1].[F_KERLCOD] AS [F_KERLCOD], 
    [Extent2].[F_SAPARTNUM] AS [F_SAPARTNUM], 
    [Extent2].[F_TYPE] AS [F_TYPE] 
    FROM [dbo].[T_SERVICESKERL] AS [Extent1] 
    INNER JOIN [dbo].[T_SERVICES] AS [Extent2] ON [Extent1].[F_SERVICESID] = [Extent2].[F_ID] 
    WHERE EXISTS (SELECT 
     1 AS [C1] 
     FROM [dbo].[T_ART] AS [Extent3] 
     WHERE (N'J' = [Extent3].[F_ACTIND]) AND ([Extent3].[F_SAPARTNUM] = [Extent2].[F_SAPARTNUM]) 
    ) 

Answer 1

为什么EF产生选择[Join1]查询[F_SERVICESID。？我不需要这个领域。

这很奇怪，如果属实，我没有解释。

谁能帮我优化下EF/Linq查询

这是值得尝试以下，这对我来说代表检索有问题的数据是最符合逻辑的方法：

KerlServices 
    .AsNoTracking() 
    .Select(ks => new { 
     ks.KerlCode, 
     ks.Service.SAPProductNumber, 
     ks.Service.Type }) 
    .Where(ks => Articles.Any(a => a.Active == "J" && a.SAPProductNumber == ks.SAPProductNumber) 
    .ToList() 

更新：最近我遇到过，当使用外键关系拨号时，EF在生成的SQL查询中包含一些附加字段。这些字段是而不是包含在预测结果中，所以我认为你不应该担心。执行上面的任何查询，在真实代码环境（VS Debug）中执行它并检查投影列表 - 我很确定相关字段不会在那里。