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Re: sequences and currval()

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On Mon, Jun 02, 2008 at 11:55:14AM -0400, Michael P. Soulier wrote:
> Hello,
> 
> I'm migrating a db schema in an automated fashion, using this
> 
> UPDATE clients_client
>     SET icp_id = null
>     WHERE icp_id = 1;
> UPDATE icps_icp
>     SET id = nextval('public.icps_icp_id_seq')
>     WHERE id = 1;
> UPDATE clients_client
>     SET icp_id = currval('public.icps_icp_id_seq')
>     WHERE icp_id = null;

Your problem is that this should be: WHERE icp_id IS NULL.

> I've noticed this on a fresh pgsql session.
> 
> tugdb=# select currval('icps_icp_id_seq');
> ERROR:  currval of sequence "icps_icp_id_seq" is not yet defined in this 
> session
> 
> I don't understand this, as I only want the current value of the 
> sequence. I suppose I can get it this way

currval() returns the value last returned by nextval() *in this
session*. If you havn't called it in this session ofcourse it won't
work. This is for transaction safety.

Have a nice day,
-- 
Martijn van Oosterhout   <kleptog@xxxxxxxxx>   http://svana.org/kleptog/
> Please line up in a tree and maintain the heap invariant while 
> boarding. Thank you for flying nlogn airlines.

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