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

"Philippe Lang" <philippe(dot)lang(at)attiksystem(dot)ch> 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.

regards, tom lane