如何将数组数据拆分到 Postgres 中的下一行答案

【问题标题】：How to split array data to next row in Postgres如何将数组数据拆分到 Postgres 中的下一行
【发布时间】：2023-01-17 17:43:50
【问题描述】：

我有一个表中的数据。我想将数组数据拆分成单独的行。

create table test1 (
  _id serial, 
  questionId character varying (50), 
  answer character varying (50), 
  subquestionId character varying (50), 
  subquestionAnswer character varying (50), 
  isActive character varying (1)
);

INSERT INTO test1 (questionid,answer,subquestionid,subquestionanswer,isactive) 
values 
('question 1','true','[100,101,102]','[[true],[false],[true]]','1'),('question 2','false','[101,106]','[[false],[true]]','1');

_id	questionid	answer	subquestionid	subquestionanswer	isactive
1	question 1	true	[100,101,102]	[[true],[false],[true]]	1
2	question 2	false	[101,106]	[[false],[true]]	1

应该需要输出。

【问题讨论】：

isActive 应该是boolean，subquestionid 和subquestionanswer 应该规范化为一对多关系。但在至少这些列应该是 text[] 或者可能组合成一个 jsonb，其中 ID 是键，标志是值。
你能用样本输入表更新你的帖子吗？
输出在链接中不可用。请在问题正文中分享。

标签： sql postgresql

【解决方案1】：

如 this answer 中所述，您可以使用转换和转换将数组的字符串表示形式转换为实际数组。（正如评论你应该不是将数组存储为字符串）

select 
   _id, 
   answer,
   translate(subquestionid, '[]', '{}')::int[] subquestionid,
   translate(subquestionanswer, '[]', '{}')::boolean[] subquestionanswer, 
   isactive
from test1;

结果

_id|answer|subquestionid|subquestionanswer      |isactive|
---+------+-------------+-----------------------+--------+
  1|true  |{100,101,102}|{{true},{false},{true}}|1       |
  2|false |{101,106}    |{{false},{true}}       |1       |

要拆分数组，请使用 unnest 并使用 WITH ORDINALITY AS 保持顺序

Finaly 将结果限制为具有相同ordinality 的行，我认为这是预期的结果，尽管与您的输出不同

with t as (
select 
   _id, 
   answer,
   translate(subquestionid, '[]', '{}')::int[] subquestionid,
   translate(subquestionanswer, '[]', '{}')::boolean[] subquestionanswer, 
   isactive
from test1
)  
select   
 t._id, 
 t.answer,
 a.subquestionid, 
 b.subquestionanswer,
 t.isactive
from t
cross join lateral unnest(subquestionid) WITH ORDINALITY AS a(subquestionid, nr)
cross join lateral unnest(subquestionanswer) WITH ORDINALITY AS b(subquestionanswer, nr)
where a.nr = b.nr


_id|answer|subquestionid|subquestionanswer|isactive|
---+------+-------------+-----------------+--------+
  1|true  |          100|true             |1       |
  1|true  |          101|false            |1       |
  1|true  |          102|true             |1       |
  2|false |          101|false            |1       |
  2|false |          106|true             |1       |

【讨论】：

以下格式的数据出现错误。插入查询新数据。 INSERT INTO test1 (questionid,answer,subquestionid,subquestionanswer,isactive) values ('question 3','true','[151,152,153,154]','[["option1"],["option1"],["option1", “选项 2”],[“选项 3”]]','1');
这值得提出一个新问题以及您对 153 的输出期望什么的解释 - 一行或两行？ @Srk

【解决方案2】：

您可以使用 string_to_array 将字符串转换为数组，并从单行生成多行，如下所示：

SELECT *
FROM (
  SELECT t._id, t.questionid, t.answer, REGEXP_REPLACE(theAnswer, '[|]|[[|]]', '') as subquestionanswer, t.isactive
  FROM   test1 t, 
       unnest(string_to_array(subquestionanswer, '],[')) theAnswer
  ) S

这应该是这样的：

SELECT t._id, t.questionid, t.answer, s.subquestionid, t.subquestionanswer, t.isactive
FROM (
  SELECT _id, questionid, answer, REGEXP_REPLACE(subquestionans, '[|]|[[|]]', '') as subquestionanswer, isactive,
  ROW_NUMBER () OVER (
           ORDER BY _id
        )
  FROM   test1, 
       unnest(string_to_array(subquestionanswer, '],[')) subquestionans
) t
inner join (
  SELECT _id , REGEXP_REPLACE(subquestion, '[|]', '') as subquestionid,
  ROW_NUMBER () OVER (
           ORDER BY _id
        )
  FROM  test1 , 
       unnest(string_to_array(subquestionid, ',')) subquestion
) s on s.ROW_NUMBER = t.ROW_NUMBER;

演示在这里：https://dbfiddle.uk/b1w3RyCJ

【讨论】：

好吧，unnest 确实保证保留顺序，但与未嵌套表的连接不会，因此对于更大的示例，您可能会弄乱 row_number 中的行顺序（with ordinaltiy 是为此目的发明的 - 请参阅另一个答案）

【解决方案3】：

感谢您的答复！

下表数据需要转换成截图格式。以前是一括号一值，现在是一括号二值。（subquestionid-153）。我已经从 Talend 中提取了这些数据。

create table test1 (_id serial, questionId character varying (50), answer character varying (50), subquestionId character varying (50), subquestionAnswer character varying (225), isActive character varying (1));

INSERT INTO test1 (questionid,answer,subquestionid,subquestionanswer,isactive) values ('question 1','true','[100,101,102]','[[true],[false],[true]]','1'),('question 2','false','[101,106]','[[false],[true]]','1');

【讨论】：