Following is a table creating script created by Entity Framework using the model shown in http://codereview.stackexchange.com/questions/14077/is-it-proper-tpt-inheritance.
In this script, there are two alter statements. What is the need for the second ALTER statement?
CREATE TABLE [dbo].[SellingItems_Book]( [Title] [nvarchar](max) NULL, [Id] [int] NOT NULL, CONSTRAINT [PK_SellingItems_Book] PRIMARY KEY CLUSTERED ( [Id] ASC )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY] ) ON [PRIMARY] GO
ALTER TABLE [dbo].[SellingItems_Book] WITH CHECK ADD CONSTRAINT [FK_Book_inherits_SellingItem] FOREIGN KEY([Id]) REFERENCES [dbo].[SellingItems] ([Id]) GO
ALTER TABLE [dbo].[SellingItems_Book] CHECK CONSTRAINT [FK_Book_inherits_SellingItem] GO