EF不同查询方法生成的SQL比较

var test1 = db.jj_RolesItem.Join(db.jj_SysItemsClass, m => m.ClassID, g => g.ClassID, (m, g) => new {m.RolesID,g.ClassName }).ToList();
var test2 = db.jj_RolesItem.Include(m => m.jj_SysItemsClass).Select(m => new {m.RolesID,m.jj_SysItemsClass.ClassName }).ToList();
var test3 = from p in db.jj_RolesItem join m in db.jj_SysItemsClass on p.ClassID equals m.ClassID select new { p.RolesID, m.ClassName };
test3.ToList();

前三条生成SQL语句相同

SELECT 
[Extent1].[RolesID] AS [RolesID], 
[Extent2].[ClassName] AS [ClassName]
FROM  [dbo].[jj_RolesItem] AS [Extent1]
INNER JOIN [dbo].[jj_SysItemsClass] AS [Extent2] ON [Extent1].[ClassID] = [Extent2].[ClassID]

var test4 = db.jj_RolesItem.First().jj_SysItemsClass.ClassName;

上面这条分两步查询：

SELECT TOP (1) 
[c].[Roles_Class_ID] AS [Roles_Class_ID], 
[c].[RolesID] AS [RolesID], 
[c].[ClassID] AS [ClassID]
FROM [dbo].[jj_RolesItem] AS [c]

exec sp_executesql N'SELECT 
[Extent1].[ClassID] AS [ClassID], 
[Extent1].[ClassName] AS [ClassName], 
[Extent1].[ParentID] AS [ParentID], 
[Extent1].[ParentPath] AS [ParentPath], 
[Extent1].[Depth] AS [Depth], 
[Extent1].[Child] AS [Child], 
[Extent1].[OrderID] AS [OrderID], 
[Extent1].[Title] AS [Title], 
[Extent1].[KeyWords] AS [KeyWords], 
[Extent1].[Description] AS [Description], 
[Extent1].[Content] AS [Content], 
[Extent1].[ShowType] AS [ShowType], 
[Extent1].[LinkUrl] AS [LinkUrl], 
[Extent1].[Intro] AS [Intro], 
[Extent1].[ClassPic] AS [ClassPic], 
[Extent1].[ItemPic] AS [ItemPic], 
[Extent1].[LanType] AS [LanType], 
[Extent1].[IsHome] AS [IsHome]
FROM [dbo].[jj_SysItemsClass] AS [Extent1]
WHERE [Extent1].[ClassID] = @EntityKeyValue1',N'@EntityKeyValue1 int',@EntityKeyValue1=106