On Mon, May 14, 2012 at 8:36 PM, Tom Lane <tgl@xxxxxxxxxxxxx> wrote:
Chris Hanks <christopher.m.hanks@xxxxxxxxx> writes:The SQL standard says not ;-).
> Nothing? Are subqueries just not meant to be used this way?
You could approximate it like this:
select ..., (select row(x,y,z) from ...), ... from ...;
as long as you don't mind pulling the composite-value output syntax
apart. This avoids the single-output-column syntactic restriction
by cramming all the values into one column.
[ thinks for a bit... ] It seems like you ought to be able to get PG
to pull the composite values apart again, with something like
select ..., (x).*, ... from
(select ..., (select row(x,y,z) from ...) as x, ...
from ... offset 0) ss;
but when I try this I get
ERROR: record type has not been registered
That's a bug, probably, but dunno how hard to fix. In the meantime you
could work around it by casting the row() _expression_ to a named
composite type; which might be a good idea anyway since there's no other
obvious way to control the column names that will be exposed by the
(x).* expansion.
regards, tom lane
Thanks, I tried playing with the row function a bit. It gave me the idea to try:
SELECT *, (SELECT ARRAY[address, (confirmed_at is not null)::text]
FROM "emails"
WHERE ("user_id" = "id")
ORDER BY "confirmed_at" DESC NULLS LAST, "created_at" DESC LIMIT 1) as best_email
FROM "users"
Since my ORM already handles Postgres arrays for me, this winds up being a bit easier to handle in my app. It's a bit ugly, but it works. I'll keep the idea of the named composite type around in case I need to revisit this later, though.
Thanks again for the advice!
