将多行结果放入单行但具有不同的列

Question

如何在不创建存储过程的情况下在oracle中实现以下功能？

Data Set:

question_id    element_id
1              7
1              8
2              9
3              10
3              11
3              12
Desired Result:

question_id    element_id1  element_id2 element_id3
1              7               8          null
2              9               null       null
3              10              11          12

Answer 1

这是一个数据透视查询，但您需要一个透视列。这就是row_number()的用武之地：

select question_id,
       max(case when seqnum = 1 then element_id end) as element_id1,
       max(case when seqnum = 2 then element_id end) as element_id2,
       max(case when seqnum = 3 then element_id end) as element_id3
from (select t.*,
             row_number() over (partition by question_id order by element_id) as seqnum
      from t
     ) t
group by question_id;