Re: "Subquery must return only one column" & query optimization

pgsql-sql-owner@postgresql.org wrote:
> "Philippe Lang"  writes:
>> I was trying to run this query this morning:
> 
>> --------------------------
>> SELECT
> 
>> r.*,
> 
>> (
>> 	SELECT
> 
>> 	rl.reminder_header,
>> 	rl.reminder_footer
> 
>> 	FROM reminder_levels AS rl
>> 	WHERE rl.lookup =
>> 	(
>> 		SELECT MAX(reminder_level_lookup)
>> 		FROM reminders
>> 		WHERE customer_id = r.customer_id
>> 	)
>> )
> 
>> FROM reminders AS r
>> --------------------------
> 
>> Postgresql replied that:
> 
>> --------------------------
>> ERROR: subquery must return only one column
> 
> Since 8.0 or so you could write the sub-select as
> 
> 	SELECT ROW(rl.reminder_header, rl.reminder_footer) FROM ...
> 
> We ought to make that happen automatically, but it's not real high on
> the to-do list. 

Hi Tom,

Fine, the query is faster now:

------------------------
SELECT 

r.*,

(SELECT 
ROW(rl.reminder_header, rl.reminder_header)
FROM reminder_levels AS rlWHERE rl.lookup =(	SELECT MAX(reminder_level_lookup) 	FROM reminders	WHERE customer_id = r.customer_id)
) AS rec

FROM reminders AS r
------------------------

... but the last column is now of type "record", and since this query
serves as a datasource for a MS Access report, it is not able to "split"
the record into the values that interest me: reminder_header and
reminder_footer!

Regards,

Philippe Lang