CREATE DATABASE NULLCHECK
GO

USE NULLCHECK
GO

-- Create abreviated table
CREATE TABLE TestTable ( [PrimaryId] UNIQUEIDENTIFIER NOT NULL DEFAULT NEWSEQUENTIALID() CONSTRAINT PK_Character PRIMARY KEY,
[SecondayId] UNIQUEIDENTIFIER NULL CONSTRAINT FK_Id1 FOREIGN KEY REFERENCES TestTable ( [PrimaryId]  ),
[TertiaryId] UNIQUEIDENTIFIER NULL CONSTRAINT FK_Id2 FOREIGN KEY REFERENCES TestTable ( [PrimaryId]  ) 
);
GO

-- Put something in it!
INSERT INTO TestTable ( [PrimaryId] ) DEFAULT VALUES ;
GO
INSERT INTO TestTable ( [PrimaryId] ) DEFAULT VALUES ;
GO
WITH Rnked AS
(
SELECT [PrimaryId], ROW_NUMBER() OVER ( ORDER BY [PrimaryId] ) AS Rnk
FROM TestTable  
)
INSERT INTO TestTable ( [SecondayId] , [TertiaryId]  )
SELECT ( SELECT [PrimaryId] FROM Rnked WHERE Rnk = 1 ), ( SELECT [PrimaryId] FROM Rnked WHERE Rnk = 2 ) ;
GO
-- Show what's in it
SELECT * FROM TestTable 
GO