Question

I am using EF4.0, and I wrote a query:

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

I need only One post from this query. I thought SingleOrDefault() will generate “SELECT TOP(1) …”, but when I look into SQL Profiler, It was:

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'

I wonder why EF result in SELECT TOP (2)? I only need one post.

Answer 1

It selects top 2 so that if there are actually 2 or more than 2 records in the database, an exception would be thrown. If it only selects top 1 there would be no way to error out.