優化實體框架的LINQ查詢（選擇1意外場）

Question

所有，

誰能幫我優化下EF/Linq查詢：

的EF/Linq查詢（從LinqPad拍攝）：

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() 

文章與服務之間的關係（ks.Service.SAPProductNumber == a.SAPProductNumber）理論上是1：可選關係，不能在EF中定義。但是，這是而不是我的問題。

產生的SQL查詢：

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] 

爲什麼EF產生選擇[Join1]查詢[F_SERVICESID]？我不需要這個領域。有誰知道一種方法來防止這種情況？

親切的問候，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() 

結果：

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] 

這種 '改進' 不回答我的問題，但肯定的結果看起來更漂亮。

更新1：

伊萬Stoev的答案查詢生成的SQL語句：

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

爲什麼EF產生選擇[Join1]查詢[F_SERVICESID。？我不需要這個領域。

這很奇怪，如果屬實，我沒有解釋。

誰能幫我優化下EF/Linq查詢

這是值得嘗試以下，這對我來說代表檢索有問題的數據是最符合邏輯的方法：

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：最近我遇到過，當使用外鍵關係撥號時，EF在生成的SQL查詢中包含一些附加字段。這些字段是而不是包含在預測結果中，所以我認爲你不應該擔心。執行上面的任何查詢，在真實代碼環境（VS Debug）中執行它並檢查投影列表 - 我很確定相關字段不會在那裏。