From: Leif Biberg Kristensen <leif@solumslekt.org>
To: pgsql-sql@postgresql.org
Subject: Re: Subselects not allowed?
Date: Sat, 11 Jun 2011 17:23:50 +0200
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On Saturday 11. June 2011 17.14.21 Tom Lane wrote:
> Guillaume Lelarge <guillaume@lelarge.info> writes:
> > On Sat, 2011-06-11 at 17:01 +0200, Leif Biberg Kristensen wrote:
> >> Can anybody tell me why this doesn't work?
> >> pgslekt=> CREATE SEQUENCE sources_source_id_seq START WITH (SELECT
> >> MAX(source_id) FROM sources);
> >> ERROR:  syntax error at or near "("
> > 
> > Because it's not supported. The START clause expects a value, not a
> > subquery.
> 
> More generally, there are no "utility" statements in PG that accept
> non-constant expressions in their parameters.  (A utility statement is
> anything other than SELECT, INSERT, UPDATE, DELETE.)
> 
> There's been occasional speculation about changing that, but it would
> take a significant amount of work I think.

Thanks for the explanation, Tom.

Presumably this means that I can't automatically patch a live database to use 
a sequence unless I build a special function for the update. With 9.x I could 
use the new DO syntax, but that isn't yet deployed everywhere.

Unless there's a way around it?

regards, Leif