not sure if it possible to change a column into identity column after it has been created.  BOL does not state this is explicitly though; all references within BOL to adding an identity column applied to new columns only.

/* --- cut here --- */

use tempdb

go

begin tran

create table orders(

id_order int

)

go

alter table orders alter column id_order int identity(1,1)

/* error here:

Server: Msg 156, Level 15, State 1, Line 1

Incorrect syntax near the keyword 'identity'.

*/

go

alter table orders add id_order2 int identity(1,1)

/* can only create identity for new columns */

go

select * from orders

rollback;

/* --- cut here --- */

Billy