Question

I need to add a autonumber column to an existing table which has about 15 million records in SQL 2005.

Do you think how much time it’ll take? What’s the better way to do it?

Answer 1

To minimize impact, I would create a new table with the identity column added, insert into the new table by selecting from the old table, then drop the old table and rename the new. I’ll give a basic outline below. Extra steps may be needed to handle foreign keys, etc.

create table NewTable (
   NewID int identity(1,1),
   Column1 ...
)
go

insert into NewTable
   (Column1, ...)
   select Column1, ...
       from OldTable
go

drop table OldTable
go

exec sp_rename 'NewTable', 'OldTable'
go