SQL Server won't let me make column identity

Question

So I have a table in SQL Server w/ a primary key column, and 4 other columns. When I modify the table, and select the primary key column to be identity, it won't let me save the table.

How can I make it an identity column through T-SQL or something without going to the UI?

Thanks.

Here's the create

USE [db]
GO

/****** Object:  Table [dbo].[tblMessages]    Script Date: 04/05/2011 11:58:25 ******/
SET ANSI_NULLS ON
GO

SET QUOTED_IDENTIFIER ON
GO

SET ANSI_PADDING ON
GO

CREATE TABLE [dbo].[tblMessages](
    [messageId] [int] NOT NULL,
    [messageText] [varchar](500) NOT NULL,
    [messageLatitude] [float] NOT NULL,
    [messageLongitude] [float] NOT NULL,
    [messageTimestamp] [datetime] NOT NULL,
PRIMARY KEY CLUSTERED 
(
    [messageId] 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

SET ANSI_PADDING OFF
GO

Answer 1

You cannot turn an existing column into an IDENTITY column after it's been created.

ALTER TABLE dbo.YourTable
  ALTER COLUMN YourColumn INT IDENTITY

will cause an error:

Msg 156, Level 15, State 1, Line 2
Incorrect syntax near the keyword 'IDENTITY'.

You need to create a new column of type INT IDENTITY and then possibly drop the old one. Or if your table is still empty: drop it and re-create it with the correct settings for your ID column

Answer 2

ALTER TABLE MyTable
ADD NewIdentity INT IDENTITY;

ALTER TABLE MyTable
DROP COLUMN OldPK;

EDIT

If your table is empty, just drop it and add IDENTITY after INT on your PK column and be done with it.