sql - 创建一个新列，其中包含另一列后续行中的值列表

Question

我有一个如下表，

并且想要创建一个新列，其中包含来自另一列后续行的值列表，如下所示，

复制粘贴: 时间戳ID值

2021-12-03 04:03:45 ID1 O

2021-12-03 04:03:46 ID1 P

2021-12-03 04:03:47 ID1问

2021-12-03 04:03:48 ID1 R

2021-12-03 04:03:49 ID1 空

2021-12-03 04:03:50 ID1 S

2021-12-03 04:03:51 ID1 T

2021-12-04 11:09:03 ID2 A

2021-12-04 11:09:04 ID2 B

2021-12-04 11:09:05 ID2 C

Answer 1

使用窗口函数和范围 JOIN:

WITH cte AS (
  SELECT tab.*, 
     COALESCE(FIRST_VALUE(CASE WHEN VALUE IS NULL THEN tmp END) IGNORE NULLS 
                OVER(PARTITION BY ID ORDER BY TMP 
                ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
             ,MAX(tmp) OVER(PARTITION BY ID)) AS next_tmp
  FROM tab
)
SELECT c1.tmp, c1.id, c1.value,
      LISTAGG(c2.value, ',') WITHIN GROUP(ORDER BY c2.tmp) AS list
FROM cte c1
LEFT JOIN cte c2
  ON c1.ID = c2.ID
 AND (c1.tmp < c2.tmp AND c2.tmp <= c1.next_tmp)
GROUP BY c1.tmp, c1.id, c1.value
ORDER BY c1.ID, c1.tmp;

<强> db<>fiddle demo

输出:

---

它是如何工作的:

这个想法是找到与每个 ID 的 NULL 值相对应的第一个时间戳:

SELECT tab.*, 
 COALESCE(FIRST_VALUE(CASE WHEN VALUE IS NULL THEN tmp END) IGNORE NULLS 
            OVER(PARTITION BY ID ORDER BY TMP 
            ROWS BETWEEN CURRENT ROW AND UNBOUNDED FOLLOWING)
         , MAX(tmp) OVER(PARTITION BY ID)) AS next_tmp
FROM tab;

输出: