Navrhoval bych, abyste upgradovali svou verzi Postgres. Všechny podporované verze podporují unnest()
:
SELECT x.*
FROM (SELECT id, UNNEST(selected_placements) as selected_placement
FROM app_data.content_cards
) x
WHERE selected_placement IS NOT NULL;
V dřívějších verzích se je můžete pokusit vybrat jeden po druhém. Následující je testováno a funguje, i když ve verzi 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;