Re: FIRST_VALUE argument must appear in group by?

On May 16, 2016, at 20:48 , David G. Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> wrote:
>
> On Monday, May 16, 2016, Guyren Howe <guyren(at)gmail(dot)com <mailto:guyren(at)gmail(dot)com>> wrote:
> I have this SELECT clause as part of a larger query:
> FIRST_VALUE(drs.id) OVER (PARTITION BY drs.order_ID ORDER BY drs.position ASC) AS current_drs_id
> Seems reasonable to me: group and sort the fields in this table and give me the first value.
>
> But I get "column "drs.id <http://drs.id/>" must appear in the GROUP BY clause or be used in an aggregate function".
>
> Huh?
>
> The larger query would help…

SELECT
o.id,
os.status AS status,
o.status_updated_at,
o.should_hold_at_airlines,
(SELECT drs2.id FROM delivery_route_segments drs2 WHERE drs2.order_id = o.id AND NOT drs2.completed ORDER BY drs2.position LIMIT 1) AS current_drs_id,

FROM
orders o JOIN
order_statuses os ON (o.status = os.id) JOIN
delivery_route_segments drs ON (drs.order_id = o.id) JOIN
pick_up_addresses pua ON (pua.order_id = o.id)
GROUP BY
o.id, os.status
I would prefer to do the subquery as a window function, both because that is cleaner to read and also because I believe it is likely to be more efficient.