How to split array into rows in Postgresql

Question

When running this query:

  SELECT id,selected_placements
  FROM  app_data.content_cards

I get a table like this:

+----+-------------------------------+
| id | selected_placements           |
+----+-------------------------------+
| 90 | {162,108,156,80,163,155,NULL} |
+----+-------------------------------+
| 91 | {}                            |
+----+-------------------------------+

What I want to do now is get this same information but with the arrays splitted into rows so I get a result like this:

+----+---------------------+
| id | selected_placements |
+----+---------------------+
| 90 | 162                 |
+----+---------------------+
| 90 | 108                 |
+----+---------------------+
| 90 | 156                 |
+----+---------------------+
| 90 | 80                  |
+----+---------------------+
| 90 | 163                 |
+----+---------------------+
| 90 | 155                 |
+----+---------------------+

As you can see I don't want to get rows with null value in "selected_placements".

I am using PostgreSQL 8.0.2.

Many thanks!

Answer 1

I would suggest that you upgrade your version of Postgres. All supported versions support 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 earlier versions, you can strive to pick them out one at a time. The following is tested and works, albeit 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;