SQL语句和LINQ返回不同数量的数据

Question

我试图将SQL语句转换为LINQ，由于某种原因，我得到的结果集是不同的。 SQL返回的数据多于LINQ。

这是SQL查询：

SELECT DISTINCT ssLookup.StopID, 
       dc.CityName, 
       dc.StateAbbrev, 
       sc.CarrierID, 
       sc.CarrierCode, 
       sc.CarrierName 
 FROM ScheduleDestinationCache dc 
INNER JOIN ScheduleStops ssFilter ON ssFilter.CarrierID = dc.CarrierID 
INNER JOIN ScheduleStops ssLookup ON dc.CityID = ssLookup.StopID 
INNER JOIN ScheduleCarriers sc ON ssLookup.CarrierID = sc.CarrierID 
WHERE (ssFilter.StopID = 582 OR ssFilter.StopID IN 
          (SELECT * FROM dbo.GetTwins(582)))
ORDER BY dc.CityName, dc.StateAbbrev

这是LINQ声明：

    (from sdc in ScheduleDestinationCaches
      let twins = GetTwins(582).Select(gt => gt.StopIDs)
     join ssFilter in ScheduleStops on sdc.CarrierID equals ssFilter.CarrierID
     join ssLookup in ScheduleStops on sdc.CityID equals ssLookup.CityID
     join sc in ScheduleCarriers on ssLookup.CarrierID equals sc.CarrierID
    where ssFilter.StopID == 582 || twins.Contains(ssFilter.StopID) 
  orderby sdc.CityName, sdc.StateAbbrev
   select new {
        ssLookup.StopID, 
        sdc.CityName, 
        sdc.StateAbbrev, 
        sc.CarrierID, 
        sc.CarrierCode, 
        sc.CarrierName
    }).GroupBy(g => new 
                    {
                       g.StopID, 
                       g.CityName, 
                       g.StateAbbrev, 
                       g.CarrierID, 
                       g.CarrierCode, 
                       g.CarrierName
                    })

我做错了什么？

提前谢谢。