BEGIN TRANSACTION
GO
CREATE TABLE dbo.Tmp_Testowners
	(
	owner_id int NOT NULL IDENTITY (1, 1),
	owname varchar(15) NULL
	)
GO
SET IDENTITY_INSERT dbo.Tmp_Testowners ON
GO
INSERT INTO dbo.Tmp_Testowners (owner_id, owname)
SELECT owner_id, owname FROM dbo.Testowners
GO
SET IDENTITY_INSERT dbo.Tmp_Testowners OFF
GO
DROP TABLE dbo.Testowners
GO
EXECUTE sp_rename N'dbo.Tmp_Testowners', N'Testowners', 'OBJECT' 
GO
COMMIT

CREATE TABLE [dbo].[Testowners](
[owner_id] [int] NULL,
[owname] [varchar](15) NULL
)
--fails: not allowed to alter an existing and add the identity property
ALTER TABLE [Testowners] ALTER COLUMN [owner_id] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY
--allowed , if the column didn't exist
ALTER TABLE [Testowners] ADD  [owner_id2] [int] IDENTITY(1,1) NOT NULL PRIMARY KEY