Hoe een array in rijen te splitsen in Postgresql

Ik raad u aan uw versie van Postgres te upgraden. Alle ondersteunde versies ondersteunen unnest() :

SELECT x.*
FROM (SELECT id, UNNEST(selected_placements) as selected_placement
      FROM  app_data.content_cards
     ) x
WHERE selected_placement IS NOT NULL;

In eerdere versies kunt u ernaar streven ze één voor één uit te kiezen. Het volgende is getest en werkt, zij het in 9.5:

with content_cards as (
     select 1 as id, array['a', 'b', 'c'] as selected_placements
    )
SELECT id, selected_placements[num] as selected_placement
FROM (SELECT cc.*, generate_series(1, ccup.maxup) as num
      FROM content_cards cc CROSS JOIN
           (SELECT MAX(ARRAY_UPPER(cc.selected_placements, 1)) as maxup
            FROM content_cards cc
           ) ccup
     ) x
WHERE selected_placements[num]  IS NOT NULL;