如何在Postgresql中將數組拆分成行

Question

運行此查詢時：

  SELECT id,selected_placements
  FROM  app_data.content_cards

我得到這樣一張桌子：

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

我現在要做的是得到相同的信息，但是將數組分成行，所以得到如下結果：

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

如您所見，我不想在“selected_placements”中獲取具有空值的行。

我正在使用PostgreSQL 8.0.2。

非常感謝！

Answer 1

我建議你升級你的Postgres版本。 所有受支持的版本都支持unnest() ：

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

在早期版本中，您可以嘗試一次選擇一個。 以下是測試和工作，雖然在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;