如何在PostgreSQL中将数组拆分为行 [英] How to split array into rows in Postgresql
本文介绍了如何在PostgreSQL中将数组拆分为行的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
运行此查询时:
SELECT id,selected_placements
FROM app_data.content_cards
我得到一个这样的表:
+----+-------------------------------+
| id | selected_placements |
+----+-------------------------------+
| 90 | {162,108,156,80,163,155,NULL} |
+----+-------------------------------+
| 91 | {} |
+----+-------------------------------+
我现在要做的是获取相同的信息,但是将数组分成几行,所以我得到这样的结果:
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 |
+----+---------------------+
如您所见,我不想在"selected_placements"中获取具有空值的行.
As you can see I don't want to get rows with null value in "selected_placements".
我正在使用PostgreSQL 8.0.2.
I am using PostgreSQL 8.0.2.
非常感谢!
推荐答案
我建议您升级Postgres版本.所有受支持的版本均支持 unnest()
:
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;
在早期版本中,您可以尝试一次将它们选出来.尽管已在9.5版中进行了测试,但仍可以正常工作:
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;
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