Valid_from Valid_to from a full loaded table - sql

Question

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 1

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: