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Re: SELECT DISTINCT ON removes results - Mailing list pgsql-general

From Geoff Winkless
Subject Re: SELECT DISTINCT ON removes results
Date
Msg-id CAEzk6fdpXWWpZxZJbhLoEC3qE-zCaFg8uXU6gxiwNZpavu30Bg@mail.gmail.com
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In response to SELECT DISTINCT ON removes results  (Guyren Howe <guyren@gmail.com>)
List pgsql-general
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On 28 October 2016 at 21:39, Guyren Howe <guyren@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
​
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​

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