entity-framework - 为什么 SQL 中 SingleOrDefault 结果为 TOP(2)？

Question

我使用的是EF4.0，我写了一个查询:

var query = context.Post.Where(p => p.Id == postId).SingleOrDefault();

我只需要此查询中的一篇文章。我以为 SingleOrDefault() 会生成“SELECT TOP(1) ...”，但是当我查看 SQL Profiler 时，它是:

exec sp_executesql N'SELECT TOP (2) 
[Extent1].[Id] AS [Id], 
[Extent1].[Title] AS [Title], 
[Extent1].[Slug] AS [Slug], 
[Extent1].[PubDate] AS [PubDate], 
[Extent1].[PostContent] AS [PostContent], 
[Extent1].[Author] AS [Author], 
[Extent1].[CommentEnabled] AS [CommentEnabled], 
[Extent1].[AttachmentId] AS [AttachmentId], 
[Extent1].[IsPublished] AS [IsPublished], 
[Extent1].[Hits] AS [Hits], 
[Extent1].[CategoryId] AS [CategoryId]
FROM [dbo].[Post] AS [Extent1]
WHERE [Extent1].[Id] = @p__linq__0',N'@p__linq__0 uniqueidentifier',@p__linq__0='ECD9F3BE-3CA9-462E-AE79-2B28C8A16E32'

我想知道为什么 EF 结果是 SELECT TOP (2)？我只需要一篇文章。

Answer 1

它选择 top 2，这样如果数据库中实际上有 2 条或多于 2 条记录，则会抛出异常。如果它只选择前 1 个，则不会出错。