EFCore中 join on的不同

當 多條件 left join on 時

LEFT OUTER JOIN

 

on new { u.UserId, ue.ExamId } equals new { sac.UserId, sac.ExamId }
into sac2
from sac in sac2.DefaultIfEmpty()

 

生成Sql 為 有空值判斷

 

 ON ([Filter1].[UserId1] = [GroupBy1].[K1]) AND (([Filter1].[ExamId2] = [GroupBy1].[K2]) OR (([Filter1].[ExamId2] IS NULL) AND ([GroupBy1].[K2] IS NULL)))

 

單條件 on 時

sql on 沒有空值判斷

 

  LEFT OUTER JOIN [dbo].[SysQuestion] AS [Extent3] ON [GroupBy1].[K1] = [Extent3].[QueId]