[postgis-users] Help, I seem to be missing a very basic concept

[Stephen Woodbridge]

Hi all,

I feel very dumb to have to ask this question, but I seem to be missing 
a very basic concept or I need more coffee to jump start my brain ...

The postGIS documentation uses a term "geometry set", which doesn't seem 
to be defined, what is this and how do I create it. I assumed it meant 
the rows resulting from a select.

But I can not get something as basic as the following to work:

select geomunion((select the_geom from county where ssccc/1000=25));

ERROR:  more than one row returned by a subquery used as an expression

select geomunion(collect((select the_geom from county where 
ssccc/1000=25)));

ERROR:  aggregate function calls may not be nested

So, how do I do something like this?

I'm using:

"PostgreSQL 8.0.4 on i386-portbld-freebsd5.3, compiled by GCC cc (GCC) 
3.4.2 [FreeBSD] 20040728"

"POSTGIS="1.0.5" GEOS="2.2.0" PROJ="Rel. 4.4.9, 29 Oct 2004" USE_STATS 
DBPROC="0.3.0" RELPROC="0.3.0""

Thanks,
   -Steve W.