如何在DB2中的一行中选择两个行值

Question

我想在一行中选择两个行值并连接。

id     value
------------
1      abc
1      def
2      ghi
3      jkl
3      mno
3      prs

结果应如下所示：

id     value
------------
1      abc, def
2      ghi
3      jkl, mno, prs

我该怎么做？

Answer 1

发布的链接@Dems在功能上与您的要求相同。

但是，如果您无法访问xml函数，那么这是一个递归CTE版本：

WITH Indexed(id, value, index) 
            as (SELECT id, value, ROW_NUMBER() OVER(PARTITION BY id ORDER BY value)
                FROM ValueTable),
     Concatenated(id, index, concatenated) 
                 as (SELECT id, index, value
                     FROM Indexed
                     WHERE index = 1
                     UNION ALL
                     SELECT a.id, a.index + 1, a.concatenated || ', ' || b.value
                     FROM Concatenated as a
                     JOIN Indexed as b
                     ON b.id = a.id
                     AND b.index = a.index + 1)
SELECT a.id, a.value
FROM Concatenated as a
EXCEPTION JOIN Indexed as b
ON b.id = a.id
AND b.index > a.index

如果初始表上有唯一索引，则Indexed CTE可以替换为对原始表的引用。