在 Snowflake 中生成日期范围

Question

我想创建两个时间戳之间的日期范围。我看到了类似的帖子，也检查了this方法。然而，仍然无法达到下面的预期输出。

请注意，如果

ended_at

为NULL，则需要取

CURRENT_TIMESTAMP

。

示例数据：

WITH t1 AS (
SELECT 'A' AS id, '2021-05-18 18:30:00'::timestamp AS started_at, '2021-05-19 09:45:00'::timestamp AS ended_at UNION ALL
SELECT 'B' AS id, '2021-05-24 11:30:40'::timestamp AS started_at, NULL::timestamp AS ended_at
    )
SELECT *
FROM t1

预期结果：

Answer 1

生成长度= datedfiff 的空格数组，拆分数组并展平以生成行。使用索引作为添加到开始日期的天数：

WITH t1 AS (
SELECT 'A' AS id, '2021-05-18 18:30:00'::timestamp AS started_at, '2021-05-19 09:45:00'::timestamp AS ended_at UNION ALL
SELECT 'B' AS id, '2021-05-24 11:30:40'::timestamp AS started_at, NULL::timestamp AS ended_at
    )
    
SELECT t1.*, dateadd(day, v.index, to_date(t1.started_at)) as date_generated 
FROM t1, 
     lateral flatten (split(space(datediff(day,to_date(t1.started_at), nvl(to_date(t1.ended_at), current_date))),' ')) v
;

结果：

ID  STARTED_AT              ENDED_AT                DATE_GENERATED
A   2021-05-18 18:30:00.000 2021-05-19 09:45:00.000 2021-05-18
A   2021-05-18 18:30:00.000 2021-05-19 09:45:00.000 2021-05-19
B   2021-05-24 11:30:40.000 null                    2021-05-24
B   2021-05-24 11:30:40.000 null                    2021-05-25

Answer 2

如果您需要生成的天数相对较少，则可以使用递归 CTE：

WITH t1 AS (
    SELECT
        'A'                              AS id,
        '2021-05-18 18:30:00'::timestamp AS started_at,
        '2021-05-19 09:45:00'::timestamp AS ended_at
    UNION ALL
    SELECT
        'B'                              AS id,
        '2021-05-24 11:30:40'::timestamp AS started_at,
        NULL::timestamp                  AS ended_at
),
     row_gen (id, started, ended, generated_day) as (
         select
             t1.id id,
             t1.started_at::date started,
             coalesce(t1.ended_at, current_timestamp)::date ended,
             started generated_day
         from t1
         union all
         select
             id,
             started,
             ended,
             dateadd('day', 1, generated_day)
         from row_gen
         where generated_day < ended
     )
SELECT *
FROM row_gen

+--+----------+----------+-------------+
|ID|STARTED   |ENDED     |GENERATED_DAY|
+--+----------+----------+-------------+
|A |2021-05-18|2021-05-19|2021-05-18   |
|A |2021-05-18|2021-05-19|2021-05-19   |
|B |2021-05-24|2021-05-25|2021-05-24   |
|B |2021-05-24|2021-05-25|2021-05-25   |
+--+----------+----------+-------------+

Answer 3

这与操作员的内容略有不同。是要求的，但对于那些希望在 Snowflake SQL 中生成日期列表的人来说很有用。

这使用 row_number 窗口函数以及 dateadd 和 generator 从开始日期开始递增。

select
  dateadd(day, row_number() over(order by 1)-1, to_date('2023-04-01')) as seq_date
from
  table(generator(rowcount => 30));

另请参阅：Lukasz Szozda 对类似问题的回答。