Linq To Sql Left outer join - filtering null results

Question

I'd like to reproduce the following SQL into C# LinqToSql

SELECT TOP(10) Keywords.*
FROM         Keywords 
LEFT OUTER JOIN IgnoreWords 
  ON Keywords.WordID = IgnoreWords.ID
WHERE  (DomainID = 16673) 
  AND (IgnoreWords.Name IS NULL)
ORDER BY [Score] DESC

The following C# Linq gives the right answer.
But I can't help think I'm missing something (a better way of doing it?)

var query = (from keyword in context.Keywords
     join ignore in context.IgnoreWords 
        on keyword.WordID equals ignore.ID into ignored
     from i in ignored.DefaultIfEmpty()
     where i == null
     where keyword.DomainID == ID
     orderby keyword.Score descending
     select keyword).Take(10);

the SQL produced looks something like this:

SELECT TOP (10) 
       [t0].[DomainID]
     , [t0].[WordID]
     , [t0].[Score]
     , [t0].[Count]
  FROM [dbo].[Keywords] AS [t0]
  LEFT OUTER JOIN 
    (  SELECT 1 AS [test]
            , [t1].[ID] 
         FROM [dbo].[IgnoreWords] AS [t1]
    ) AS [t2] 
    ON [t0].[WordID] = [t2].[ID] 
WHERE ([t0].[DomainID] = 16673) 
  AND ([t2].[test] IS NULL)
ORDER BY [t0].[Score] DESC

How can I get rid of this redundant inner selection? It's only slightly more expensive but every bit helps!

Answer 1

I think you can do something like this to eliminate the left join and maybe get more efficiency:

var query = (from keyword in context.Keywords
             where keyword.DomainID == ID 
             && !(from i in context.IgnoreWords select i.ID).Contains(keyword.WordID)
             orderby keyword.Score descending
             select keyword)
            .Take(10);