Valid_from Valid_to 来自满载 table

Question

有一个来源 table 可以按月完整加载数据。 table 如下例所示。

来源table:

pk	code_paym	code_terms	etl_id
1	2	3	2020-08-01
1	2	3	2020-09-01
1	2	4	2020-10-01
1	2	4	2020-11-01
1	2	4	2020-12-01
1	2	4	2021-01-01
1	2	3	2021-02-01
1	2	3	2021-03-01
1	2	3	2021-04-01
1	2	3	2021-05-01

我想从源 table 创建 valid_from valid_to 列，如下例所示。

期望的输出：

pk	code_paym	code_terms	valid_from	valid_to
1	2	3	2020-08-01	2020-09-01
1	2	4	2020-10-01	2021-01-01
1	2	3	2021-02-01	2021-05-01

可以看出，到时候属性可以恢复到相同的值。如何通过 sql 代码实现此输出？

非常感谢，问候

Answer 1

使用CONDITIONAL_TRUE_EVENT窗函数确定连续子组：

CREATE OR REPLACE TABLE t( pk INT,  code_paym INT,  code_terms INT,     etl_id DATE)
AS
          SELECT 1,     2,  3,  '2020-08-01'
UNION ALL SELECT 1,     2,  3,  '2020-09-01'
UNION ALL SELECT 1,     2,  4,  '2020-10-01'
UNION ALL SELECT 1,     2,  4,  '2020-11-01'
UNION ALL SELECT 1,     2,  4,  '2020-12-01'
UNION ALL SELECT 1,     2,  4,  '2021-01-01'
UNION ALL SELECT 1,     2,  3,  '2021-02-01'
UNION ALL SELECT 1,     2,  3,  '2021-03-01'
UNION ALL SELECT 1,     2,  3,  '2021-04-01'
UNION ALL SELECT 1,     2,  3,  '2021-05-01';

查询：

WITH cte AS (
  SELECT t.*, 
    CONDITIONAL_TRUE_EVENT(CODE_TERMS != LAG(CODE_TERMS,1,CODE_TERMS)
                                   OVER(PARTITION BY PK, CODE_PAYM ORDER BY ETL_ID)) 
    OVER(PARTITION BY PK, CODE_PAYM ORDER BY ETL_ID) AS grp 
  FROM t 
)
SELECT PK, CODE_PAYM, grp, MIN(ETL_ID) AS valid_from, MAX(ETL_ID) AS valid_to
FROM cte
GROUP BY PK, CODE_PAYM, grp;

输出：

Valid_from Valid_to 来自满载 table

Valid_from Valid_to from a full loaded table

sql

snowflake-cloud-data-platform

etl

gaps-and-islands