sql or pgsql question, accessing a created value - Mailing list pgsql-general

Hope someone's out there for this one.  Basically I'm creating a summary table of many
underlying tables in one select statement ( though that may have to change ).  My problem
can be shown in this example..

select my_function( timeofmeasurement, longitude ) as solarnoon,
        extract(epoch from ( timeofmeasurement - solarnoon ) as solardiff
        ( case when solardiff < 3600 then 'Y' else 'N' end ) as within_solar_hour
from
    my_table;

But I get an error along the lines of
ERROR:  column "solarnoon" does not exist
LINE 8:  extract(epoch from (timeofmeasurement - solarnoon) ) as sola...

It's probably a compile-time run-time sort of chicken and egg thing. ;)

So I' off onto pl/pgsql, but still not having much luck.  Full under construction
sql right now is:



create or replace function load_air_temp_summary()
returns void as $$
declare solarnoon timestamp;
         solardiff interval;
BEGIN
select count(*) from (
select
  aird.current_temp, aird.minimum_temp, aird.measured_at,
  subd.datum_id, subd.datum_type,
  subm.person_id, subm.site_id,
  loc.latitude, loc.longitude,
  select solarnoon( aird.measured_at, loc.longitude ) INTO solarnoon  <-- ** trying to save the value
  from air_temp_data aird,
      submission_data subd,
      submissions subm,
      sites sites,
      locations loc
where
  subd.datum_type = 'AirTempDatum' and
  subd.datum_id = aird.id and
  subd.submission_id = subm.id and
  subm.site_id = sites.id and
  loc.locatable_type = 'Site' and
  sites.id = loc.locatable_id
) as fred;
END $$ LANGUAGE plpgsql;

but it dislikes the third "select" stmt, or if I remove that select stmt, I get

ERROR:  syntax error at or near "("
LINE 1: ...d, subm.site_id, loc.latitude, loc.longitude,  $1 ( aird.mea...


Any tips or tricks on how I should approach this are appreciated. How do I store
and use values that are calculated on the fly.

-ds