重叠生效日期聚合

Question

我正在尝试汇总重叠的生效日期。日期之间的任何间隔都应视为单独的行。我正在使用最小值和最大值，但我的输出低于预期，但希望看到预期的输出。

我的查询

WITH test_data AS (
    SELECT '2020-01-01' AS date_from,
           '2020-01-03' AS date_to,
           '1'          AS product
    UNION ALL
    SELECT '2020-01-05' AS date_from,
           '2020-01-07' AS date_to,
           '1'          AS product
    UNION ALL
    SELECT '2020-01-06' AS date_from,
           '2020-01-10' AS date_to,
           '1'          AS product
)
SELECT product,
       MIN(date_from) AS date_from,
       MAX(date_to)   AS date_to
FROM test_data
GROUP BY 1;

---

源数据

date_from	date_to	product
2020-01-01	2020-01-03	1
2020-01-05	2020-01-07	1
2020-01-06	2020-01-10	1

---

输出表

date_from	date_to	product
2020-01-01	2020-01-10	1

---

预期输出

date_from	date_to	product
2020-01-01	2020-01-03	1
2020-01-05	2020-01-10	1

---

提前致谢！

Answer 1

这是一种孤岛问题。我推荐这样的方法：

SELECT product,
       MIN(date_from) AS date_from,
       MAX(date_to)   AS date_to
FROM (SELECT td.*,
             SUM(CASE WHEN prev_date_to >= date_from THEN 0 ELSE 1 END) OVER (PARTITION BY product ORDER BY date_to) as grp
      FROM (SELECT td.*,
                   MAX(date_to) OVER (PARTITION BY product ORDER BY date_from ROWS BETWEEN UNBOUNDED PRECEDING AND 1 PRECEDING) as prev_date_to
            FROM test_data td
           ) td
     ) td
GROUP BY grp, product
ORDER BY product, MIN(date_from);

Here 是一个 dbfiddle。

这是在做什么？最里面的子查询获取前行的最新date_to。这用于确定每一行是否“连接”到前一行，或者是否开始一个新的分组。

中间子查询的逻辑是行开始新组时的累积总和。然后，外部查询按此分组进行聚合。

Answer 2

日期范围的合并可以通过MATCH_RECOGNIZE实现。

数据准备：

CREATE OR REPLACE TABLE test_data AS
SELECT '2020-01-01'::DATE AS date_from, '2020-01-03'::DATE AS date_to, '1'  AS product
UNION ALL
SELECT '2020-01-05'::DATE AS date_from, '2020-01-07'::DATE AS date_to, '1'  AS product
UNION ALL
SELECT '2020-01-06'::DATE AS date_from, '2020-01-10'::DATE AS date_to, '1' AS product;

查询：

SELECT * 
FROM test_data t
MATCH_RECOGNIZE(
  PARTITION BY product
  ORDER BY date_from, date_to
  MEASURES FIRST(date_from) date_from, MAX(date_to) date_to
  PATTERN(a* b)
  DEFINE a AS MAX(date_to) OVER() >= NEXT(date_from)
) mr;

db<>fiddle demo - Oracle

相关阅读：Merging Overlapping Date Ranges with MATCH_RECOGNIZE by stewashton