On 28 October 2016 at 21:39, Guyren Howe <guy...@gmail.com> wrote: > Using 9.5, this query: > > SELECT o.id, > a.number AS awb > FROM pt.orders o > LEFT JOIN ( > SELECT DISTINCT ON ((string_agg(air_way_bills.number::text, > ','::text))) > string_agg(air_way_bills.number::text, ','::text) AS number, > air_way_bills.order_id > FROM pt.air_way_bills > GROUP BY air_way_bills.order_id) a ON a.order_id = o.id > > From https://www.postgresql.org/docs/9.5/static/sql-select. html#SQL-DISTINCT
The DISTINCT ON expression(s) must match the leftmost ORDER BY expression(s). The ORDER BY clause will normally contain additional expression(s) that determine the desired precedence of rows within each DISTINCT ON group. Does the problem go away if you do that? Geoff
