A couple of Linq to Sql Query Examples

Just a quick reference of a couple basic query conversions for Linq to SQL

Code Snippet

21. //inner join
22.             //SELECT [t0].[CountyName]
23.             //FROM [dbo].[County] AS [t0]
24.             //INNER JOIN [dbo].[State] AS [t1] ON [t0].[StateID] = [t1].[StateID]
25.             //WHERE LOWER([t1].[StateName]) = @p0
26.             var counties =  from c in db.Counties
27.                             join st in db.States on c.StateID equals st.StateID
28.                             where st.StateName.ToLower().Equals("florida")
29.                             select c.CountyName;
30.  
31.  
32.             //left join -- use DefaultIfEmpty and new object
33.             //SELECT [t0].[CountyName],
34.             //(CASE WHEN [t2].[test] IS NULL THEN CONVERT(NVarChar(50),@p0)
35.             //      ELSE CONVERT(NVarChar(50),[t2].[StateName])
36.             //      END) AS [StateName]
37.             //FROM [dbo].[County] AS [t0]
38.             //LEFT OUTER JOIN
39.             //(
40.             //      SELECT 1 AS [test], [t1].[StateID], [t1].[StateName]
41.             //      FROM [dbo].[State] AS [t1]
42.             //) AS [t2] ON [t0].[StateID] = [t2].[StateID]
43.             var counties2 = from c in db.Counties
44.                             join st in db.States on c.StateID equals st.StateID
45.                             into stateCounties
46.                             from co in stateCounties.DefaultIfEmpty()
47.                             select new { CountyName = c.CountyName, StateName = (co == null)? "": co.StateName };
48.  
49.  
50.             //Same table query
51.             //SELECT [t0].[CountyName]
52.             //FROM [dbo].[County] AS [t0],
53.             //     [dbo].[County] AS [t1]
54.             //WHERE ([t0].[CountyName] = [t1].[CountyName]) AND ([t0].[CountyID] <> [t1].[CountyID])
55.             var counties3 = from c1 in db.Counties
56.                             from c2 in db.Counties
57.                             where c1.CountyName == c2.CountyName && c1.CountyID != c2.CountyID
58.                             select new
59.                             {
60.                                 CountyName = c1.CountyName,
61.                             };
62.  
63.  
64.  
65.  
66.             var counties4 = (from c1 in db.Counties
67.                             from c2 in db.Counties
68.                             where c1.CountyName == c2.CountyName && c1.CountyID != c2.CountyID
69.                             group c1 by c1.CountyName into dups
70.                             select new
71.                             {
72.                                 CountyName = dups.Key,
73.                                 Count = dups.Count()
74.                             }
75.                             ).OrderBy(n => n.CountyName);

Some resources I found useful:
http://codesamplez.com/database/linq-to-sql-join-tutorials
http://weblogs.asp.net/rajbk/archive/2010/03/12/joins-in-linq-to-sql.aspx
http://msdn.microsoft.com/en-us/library/bb386913.aspx
   More specifically to joins:
   http://msdn.microsoft.com/en-us/library/bb399397.aspx