[英]PostgreSQL multiple row as columns
I have a table like this: 我有一张这样的桌子:
| id | name | segment | date_created | question | answer |
|----|------|---------|--------------|----------|--------|
| 1 | John | 1 | 2018-01-01 | 10 | 28 |
| 1 | John | 1 | 2018-01-01 | 14 | 37 |
| 1 | John | 1 | 2018-01-01 | 9 | 83 |
| 2 | Jack | 3 | 2018-03-11 | 22 | 13 |
| 2 | Jack | 3 | 2018-03-11 | 23 | 16 |
And I want to show this information in a single row, transpose all the questions and answers as columns: 我想在单行中显示此信息,将所有问题和答案换成列:
| id | name | segment | date_created | question_01 | answer_01 | question_02 | answer_02 | question_03 | answer_03 |
|----|------|---------|--------------|-------------|-----------|-------------|-----------|-------------|-----------|
| 1 | John | 1 | 2018-01-01 | 10 | 28 | 14 | 37 | 9 | 83 |
| 2 | Jack | 3 | 2018-03-11 | 22 | 13 | 23 | 16 | | |
The number os questions/answers for the same ID is known. 相同ID的问题/答案的数量是已知的。 Maximum of 15.
最多15。
I'm already tried using crosstab, but it only accepts a single value as category and I can have 2 (question/answer). 我已经尝试使用交叉表,但是它只接受一个值作为类别,并且我可以有2个(问题/答案)。 Any help how to solve this?
任何帮助如何解决这个问题?
You can try to use row_number
to make a number in subquery then, do Aggregate function condition in the main query. 您可以尝试使用
row_number
在子查询中生成一个数字,然后在主查询中执行Aggregate函数条件。
SELECT ID,
Name,
segment,
date_created,
max(CASE WHEN rn = 1 THEN question END) question_01 ,
max(CASE WHEN rn = 1 THEN answer END) answer_01 ,
max(CASE WHEN rn = 2 THEN question END) question_02,
max(CASE WHEN rn = 2 THEN answer END) answer_02,
max(CASE WHEN rn = 3 THEN question END) question_03,
max(CASE WHEN rn = 3 THEN answer END) answer_03
FROM (
select *,Row_number() over(partition by ID,Name,segment,date_created order by (select 1)) rn
from T
) t1
GROUP BY ID,Name,segment,date_created
[Results] : [结果] :
| id | name | segment | date_created | question_01 | answer_01 | question_02 | answer_02 | question_03 | answer_03 |
|----|------|---------|--------------|-------------|-----------|-------------|-----------|-------------|-----------|
| 1 | John | 1 | 2018-01-01 | 1 | 28 | 14 | 37 | 9 | 83 |
| 2 | Jack | 3 | 2018-03-11 | 22 | 13 | 23 | 16 | (null) | (null) |
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