實體框架生成不同的SQL查詢

我有下面的代碼，用於從表實體框架生成不同的SQL查詢

var a = db.Customs 
      .Where(x => x.Cust_ID == tid) 
      .Select(x => x.TransferCommission.Value) 
      .FirstOrDefault().ToString();

獲得一個場，該代碼生成低於SQL查詢

SELECT TOP (1) 
[Extent1].[TransferCommission] AS [TransferCommission] 
FROM [dbo].[Custom] AS [Extent1] 
WHERE 54612 = [Extent1].[Cust_ID]

但是這個代碼

var b = db.Tours 
      .Where(x => x.Tour_ID == tid) 
      .Select(x => x.Supl_ID.Value) 
      .FirstOrDefault() 
      .ToString();

生成以下SQL查詢

exec sp_executesql N'SELECT 
[Limit1].[Supl_ID] AS [Supl_ID] 
FROM (SELECT TOP (1) 
    [Extent1].[Supl_ID] AS [Supl_ID] 
    FROM (SELECT 
[Toursn].[Airline_ID] AS [Airline_ID], 
[Toursn].[Tour_Code] AS [Tour_Code], 
[Toursn].[Supl_ID] AS [Supl_ID], 
[Toursn].[Start_Destination_ID] AS [Start_Destination_ID], 
[Toursn].[End_Destination_ID] AS [End_Destination_ID], 
[Toursn].[Tour_Name] AS [Tour_Name], 
[Toursn].[Service_Category_ID] AS [Service_Category_ID], 
[Toursn].[Tour_Option_Name] AS [Tour_Option_Name], 
[Toursn].[Run_MinPax] AS [Run_MinPax], 
[Toursn].[Notes] AS [Notes], 
[Toursn].[Advse_Book] AS [Advse_Book], 
[Toursn].[Tour_Desc] AS [Tour_Desc], 
[Toursn].[Tour_Duration] AS [Tour_Duration], 
[Toursn].[Distance] AS [Distance], 
[Toursn].[Tour_ID] AS [Tour_ID], 
[Toursn].[Tour_Map1] AS [Tour_Map1], 
[Toursn].[Tour_Num_Days_Cruise] AS [Tour_Num_Days_Cruise], 
[Toursn].[Tour_Itinerary_File] AS [Tour_Itinerary_File], 
[Toursn].[Cruise_Supl_ID] AS [Cruise_Supl_ID], 
[Toursn].[Toursn_Deleted] AS [Toursn_Deleted], 
[Toursn].[Tour_Picture] AS [Tour_Picture], 
[Toursn].[motherTour_ID] AS [motherTour_ID], 
[Toursn].[isMotherTour] AS [isMotherTour], 
[Toursn].[Tour_cruise_before_day] AS [Tour_cruise_before_day], 
[Toursn].[Tour_Thumbnail] AS [Tour_Thumbnail], 
[Toursn].[MainNotification] AS [MainNotification], 
[Toursn].[Operated_Supl_ID] AS [Operated_Supl_ID], 
[Toursn].[TransferStatus] AS [TransferStatus], 
[Toursn].[Escor] AS [Escor], 
[Toursn].[OnList] AS [OnList], 
[Toursn].[PicUploadDate] AS [PicUploadDate], 
[Toursn].[TransCat] AS [TransCat], 
[Toursn].[TransferNo] AS [TransferNo], 
[Toursn].[TransferDuration] AS [TransferDuration], 
[Toursn].[DeparTime] AS [DeparTime], 
[Toursn].[ArrivTime] AS [ArrivTime], 
[Toursn].[Educational] AS [Educational], 
[Toursn].[Tour_Picture_AltTag] AS [Tour_Picture_AltTag], 
[Toursn].[OnlyBookingAgent] AS [OnlyBookingAgent], 
[Toursn].[DuplicateDate] AS [DuplicateDate], 
[Toursn].[Duplicate] AS [Duplicate], 
[Toursn].[DuplicateNo] AS [DuplicateNo], 
[Toursn].[Toursn_CruiseCnt] AS [Toursn_CruiseCnt] 
FROM [dbo].[Toursn] AS [Toursn]) AS [Extent1] 
    WHERE ([Extent1].[Tour_ID] = @p__linq__0) AND (@p__linq__0 IS NOT NULL) 
) AS [Limit1]',N'@p__linq__0 int',@p__linq__0=25

我不明白爲什麼會發生？任何人都可以幫助我解決這個問題嗎？

來源

2014-01-07 ypbr

其在'Toursn'表格中的字段數目使其看起來很戲劇化。但是，如果將這些消除掉，則只剩下幾乎相同的查詢。只是簡單子查詢的前1個，而不是表格的前1個。 – paqogomez

「Cust_ID」和「Tour_ID」列的數據庫和EF類型是什麼？ – MarcinJuraszek

感謝每一個。我發現了這個問題。可能是我的錯誤，但我不是創建數據庫，所以我錯過了遊覽表沒有主鍵。

我將Tour_ID字段分配爲主鍵，它的工作很好。

來源

2014-01-08 09:42:52 ypbr

實體框架生成不同的SQL查詢

回答

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