組連接多個錶轉換SQL到Linq

任何人都可以通過將此SQL語句轉換爲Linq來幫助我嗎？組連接多個錶轉換SQL到Linq

SELECT a.KPI, a.ProcessDate, a.Actual, lf.LPLocal, pf.LPProd, d.LocalDelta, d.ProdDelta 
FROM 
    Actual AS a 
    LEFT OUTER JOIN Local l ON l.Date = a.Date 
    LEFT OUTER JOIN Prod p ON p.Date = a.Date 
    LEFT OUTER JOIN Delta d ON d.Date = a.Date

我做了一些研究，並與此想出了：

Dim Xq1 = (From a In tmpActual _ 
Group Join l In tmpLocal On l.Item("Dates") Equals a.Item("Dates") Into al = Group _ 
From x In al.DefaultIfEmpty() _ 
Group Join p In tmpProd On p.Item("Dates") Equals a.Item("Dates") Into ap = Group _ 
     From y In ap.DefaultIfEmpty() _ 
Group Join d In tmpDelta On d.Item("Dates") Equals a.Item("Dates") Into ad = Group _ 
From z In ad.DefaultIfEmpty() _ 
Select 
    KPI = a.Item("KPI"), ProcessDate = a.Item("Dates"), 
    AccountingActual = a.Item("AccountingActual"), 
    LocalForecast = x.Item("LocalForecast"), 
    ProdForecast = y.Item("ProdForecast"), 
    Localdelta = z.Item("LocalDelta"), 
    ProdDelta = z.Item("ProdDelta")).DefaultIfEmpty

但是，當我跑了它，它有：

System.InvalidCastException被抓獲消息=「無法類型 'd__9e 1[VB$AnonymousType_6 7 [System.Object，System.Object，System.Object，System.Object，System.Object，System.Object，System.Object]]' 類型'Syste m.Data.DataTable」。」用C 在LPBenchmarking.BLL.GetKPIFromPrime（PreKPIData DS，離羣值的Int32）：：
源= 「LPBenchmarking」棧跟蹤\文件和設置\ RSpalding.TCI \我文檔\庫\文件\ 2008的Visual Studio \項目\ LPB 優化\ LPBenchmarking_Web \ BusinessComponents \ BLL.vb：行 204的InnerException：

任何幫助，將不勝感激。謝謝。

來源

2011-03-07 Richard Spalding

請注意，您的原始SQL不使用分組方式，並且存在拼寫錯誤：lf。和pf。應該是l。和p。想必。 – 2011-03-11 11:55:54

嘗試劈裂查詢成若干子查詢，看看哪些工作（如果有的話）：

Dim alq = From a In tmpActual _ 
Group Join l In tmpLocal On l.Item("Dates") Equals a.Item("Dates") Into al = Group 

Dim apq = _ 
From x In alq.DefaultIfEmpty() _ 
Group Join p In tmpProd On p.Item("Dates") Equals a.Item("Dates") Into ap = Group 

Dim adq = _ 
      From y In apq.DefaultIfEmpty() _ 
Group Join d In tmpDelta On d.Item("Dates") Equals a.Item("Dates") Into ad = Group 

Dim Xq = _ 
From z In adq.DefaultIfEmpty() _ 
Select 
    KPI = a.Item("KPI"), 
    ProcessDate = a.Item("Dates"), 
    AccountingActual = a.Item("AccountingActual"), 
    LocalForecast = x.Item("LocalForecast"), 
    ProdForecast = y.Item("ProdForecast"), 
    Localdelta = z.Item("LocalDelta"), 
    ProdDelta = z.Item("ProdDelta") 

Dim Xq1 = Xq.DefaultIfEmpty

注我只是編輯您的SO提供的代碼 - 我沒有語法在IDE中檢查它！

來源

2011-03-11 12:07:00

組連接多個錶轉換SQL到Linq

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