Linq to sql：继承与关系-技术开发专区

Linq to sql：继承与关系

作者：lovecherry博客编辑： nancy 2008-01-25 00:00

查询经过改造后会得到下面的SQL：

SELECT [t0].[CategoryID], [t0].[CategoryName], [t1].[BoardID], [t1].[BoardName], [t1].[BoardCategory], (
SELECT COUNT(*)
FROM [Boards] AS [t3]
WHERE [t3].[BoardCategory] = [t0].[CategoryID]
) AS [count]
FROM [Categories] AS [t0]
LEFT OUTER JOIN [Boards] AS [t1] ON [t1].[BoardCategory] = [t0].[CategoryID]
WHERE ((
SELECT COUNT(*)
FROM [Boards] AS [t2]
WHERE [t2].[BoardCategory] = [t0].[CategoryID]
)) > @p0
ORDER BY [t0].[CategoryID], [t1].[BoardID]
-- @p0: Input Int32 (Size = 0; Prec = 0; Scale = 0) [2]

在添加分类的时候，如果这个分类下还有新的版块，那么提交新增分类的时候版块也会新增：

BoardCategory dbcat = new BoardCategory() { CategoryName = "Database" };
Board oracle = new Board() { BoardName = "Oracle", Category = dbcat};
ctx.BoardCategories.Add(dbcat);
ctx.SubmitChanges();

上述代码导致下面的SQL被执行：

INSERT INTO [Categories]([CategoryName]) VALUES (@p0)
SELECT [t0].[CategoryID]
FROM [Categories] AS [t0]
WHERE [t0].[CategoryID] = (SCOPE_IDENTITY())
-- @p0: Input AnsiString (Size = 8; Prec = 0; Scale = 0) [Database]

INSERT INTO [Boards]([BoardName], [BoardCategory]) VALUES (@p0, @p1)
SELECT [t0].[BoardID]
FROM [Boards] AS [t0]
WHERE [t0].[BoardID] = (SCOPE_IDENTITY())
-- @p0: Input AnsiString (Size = 6; Prec = 0; Scale = 0) [Oracle]

-- @p1: Input Int32 (Size = 0; Prec = 0; Scale = 0) [23]

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