Why create a foreign key constraint that references the primary key of the same table from the primary key field

Question

I inherited a SQL Server database that has a table with a primary key named RecordID. The table definition and the foreign key defined like this:

CREATE TABLE [dbo].[MyTable](
  [RecordId] [int] IDENTITY(1,1) NOT NULL,
  [FileName] [nvarchar](255) NOT NULL,
  [Record] [nvarchar](255) NOT NULL,
  [ErrorDescription] [nvarchar](255) NULL,
  [ProcessDate] [datetime] NOT NULL,
 CONSTRAINT [PK_MyTable] PRIMARY KEY CLUSTERED 
(
  [RecordId] ASC
)WITH (PAD_INDEX  = OFF, STATISTICS_NORECOMPUTE  = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS  = ON, ALLOW_PAGE_LOCKS  = ON, FILLFACTOR = 90) ON [PRIMARY]
) ON [PRIMARY]

GO

ALTER TABLE [dbo].[MyTable]  WITH CHECK ADD  CONSTRAINT [FK_MyTable_MyTable] FOREIGN KEY([RecordId])
REFERENCES [dbo].[MyTable] ([RecordId])
GO

ALTER TABLE [dbo].[MyTable] CHECK CONSTRAINT [FK_MyTable_MyTable]
GO

I could understand this if the foreign key referenced from a different field in the same table back to the primaray key field which would allow for a heirarchy, but in this case the two fields in the foreign key definition are exactly the same field. Is this just a mistake in the original definition of the table and foreign key? Or is there a real advantage somehow to this?

Thanks in advance for your time in replying.

Getup

Maybe check if there's another table in the database that looks like it should be referencing this table but isn't. – Wield

Answer 1

Because the foreign key references itself, the check can never fail. That makes it, as a constraint, a no-op, so it is in every sense of the word, extraneous. Someone clearly made a mistake in creating the constraint.

I thought I might be missing something, so a quick check turned up with this: http://www.dotnetnuke.com/Resources/Forums/forumid/-1/postid/342163/scope/posts.aspx which reinforces my suspicion (user error). My most educated conclusion is that someone at some stage thought of creating a self-referencing (other column) table constraint, but in a wicked twist of confusion created this abomination.

Toll