SQL Server 2008 : ALTER IDENTITY TYPE

Question

I have an existing table MCheckTypes and it has a primary key column ID. What I want to do is to alter the table to add identity type on the primary key. I don't want to drop a table and recreate a new one. I already google it but no luck. Below is my script

ALTER TABLE MCheckTypes 
   ALTER COLUMN [ID] INT IDENTITY(1, 1) NOT NULL

below is the error message

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

Answer 1

You cannot "convert" an existing column into an IDENTITY column - you have to create a new column as INT IDENTITY:

ALTER TABLE MCheckTypes 
ADD NewID INT IDENTITY (1, 1) NOT NULL;