Re: SELECT DISTINCT ON removes results

[Geoff Winkless <pgsqladmin@xxxxxxxx>]

On 28 October 2016 at 21:39, Guyren Howe <guyren@xxxxxxxxx> 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​