Alter exisitng int column to identity in sybase

Question

Sybase 12.5

I have an existing table in production that needs it's PK int column to be altered such that it is auto populated - when the table was created it would ideally have had the ID column created as an Identity. This ID column is a foreign key in multiple other tables so deleting the table and starting again isn't an option. Problem is, I can't set the PK as an IDENTITY, and creating a temp column with the current values and copying these to a new IDENTITY column is also failing.

As the ID column is already populated, I can't simply turn this column into an IDENTITY (at least, I haven't found any SQL that will do this).

I have created a copy of the table, with an additional column holding the current PK value (division_id_tmp).

CREATE TABLE division_tmp
(
   division_id int IDENTITY NOT NULL 
   division_id_tmp int,      
   description varchar(255) NOT NULL,
   is_active tinyint DEFAULT 1 NOT NULL,
)

When i try to enter a datascript from the original table

INSERT INTO division_tmp
(description,is_active,division_id_tmp,division_id) 
VALUES 
('TEST',1,36,34)

I get the following error:

Error: Explicit value specified for identity field in table 'division_tmp' 
when 'SET IDENTITY_UPDATE' is OFF.

If I run the statement:

SET IDENTITY_INSERT division_tmp OFF

The statement executes without complaint, but attempts to insert the datascript result in the same error as above. If I run the statement

SET IDENTITY_INSERT ac_division_lookup_awd ON

I get the error

Error: Unable to 'SET IDENTITY_INSERT' for table '**division_tmp**' because 
IDENTITY_INSERT or IDENTITY_UPDATE is already ON for the table '**division**' in 
database 'preserve'.

I can't be the first person who's experienced this problem? Any ideas on where I'm going wrong?

Thanks

Answer 1

Solved it. Think the underlying issue is I am a tool.

Getting confused between:

IDENTITY_INSERT 

and

IDENTITY_UPDATE

So, what I need to do is:

alter table division add division_id_tmp int IDENTITY not null 
SET IDENTITY_UPDATE division ON
update division set division_id_tmp = division_id
SET IDENTITY_UPDATE division OFF
alter table division drop division_id
EXEC sp_rename 
    @objname = 'division.division_id_tmp', 
    @newname = 'division_id', 
    @objtype = 'COLUMN'

Job done!