Valid_from Valid_to from a full loaded table

There is a source table which loads the data full and monthly. The table looks like below example.

Source 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

I would like to create valid_from valid_to columns from the source table like below example.

Desired Output:

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

As it can be seen attributes can go back to the same values by the time. How can I make this output happen by sql code?

Thank you very much, Regards

Answer

Using CONDITIONAL_TRUE_EVENT windowed function to determine continuous subgroups:

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';

Query:

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;

Output: