Re: How-To: Aggregate data from multiple rows into a delimited list.

> The query would become
>  SELECT a.id, a.name, array_acc(b.name) as b_names
>  FROM a LEFT JOIN b USING(id)
>  GROUP BY a.id, a.name;
>

All variants are possible. Variant with array_to_string is faster and
doesn't need own aggregate function. And you can easy remove
duplicities.

SELECT a.id, a.name,
      ARRAY_TO_STRING(ARRAY(
        SELECT DISTINCT b.name
        FROM b
        WHERE b.id = a.id
        ORDER BY b.name ASC
      ), ',') AS b_names
    FROM a
    ORDER BY a.id ASC;

regards
Pavel