Group customer transactions based on the subsequent transaction

Question

Small change in the requirement

Needed Teradata SQL query to create a grouping from the first transaction to its subsequent transactions. If a subsequent transaction is made within 30 days of the previous transaction, consider them all to belongs to the same group. Break the group and start a new one if any transaction is made more than 30 days after the previous transaction.

data:

trans_Id	customer_id	trans_date
001	1101	2020-11-02
002	1101	2020-11-14
003	1101	2020-11-18
004	1101	2021-12-04
005	1101	2021-01-06
006	1101	2021-01-08
007	1101	2021-02-17
008	1101	2021-03-01
009	1101	2021-03-04
010	1102	2021-03-02
011	1102	2021-03-08
012	1102	2021-04-01
013	1102	2021-04-02
014	1102	2021-04-12
015	1102	2021-04-29
016	1102	2021-06-10
017	1102	2021-06-12

Expected result (expecting grouping like below). from 001 till 004 fall under within 30 day to its previous transaction. 005 has elapsed 30 day from it's previous transaction so new group has to be started.

trans_Id	customer_id	trans_date	Group
001	1101	2020-11-02	1
002	1101	2020-11-14	1
003	1101	2020-11-18	1
004	1101	2021-12-04	1
005	1101	2021-01-06	2
006	1101	2021-01-08	2
007	1101	2021-02-17	3
008	1101	2021-03-01	3
009	1101	2021-03-04	3
010	1102	2021-03-02	1
011	1102	2021-03-08	1
012	1102	2021-04-01	2
013	1102	2021-04-02	2
014	1102	2021-04-12	2
015	1102	2021-04-29	2
016	1102	2021-06-10	3
017	1102	2021-06-12	3

Answer 1

From Oracle 12, you can use MATCH_RECOGNIZE to perform row-by-row pattern matching:

SELECT *
FROM   table_name
MATCH_RECOGNIZE(
  PARTITION BY customer_id
  ORDER BY trans_date
  MEASURES
    MATCH_NUMBER() AS grp
  ALL ROWS PER MATCH
  PATTERN ( within_30_days+ )
  DEFINE
    within_30_days AS trans_date <= FIRST(trans_date) + INTERVAL '30' DAY
)

Which, for the sample data:

CREATE TABLE table_name (trans_id, customer_id, trans_date) AS
  SELECT '001', '1101',  DATE '2020-11-02' FROM DUAL UNION ALL
  SELECT '002', '1101',  DATE '2020-11-14' FROM DUAL UNION ALL
  SELECT '003', '1101',  DATE '2020-11-18' FROM DUAL UNION ALL
  SELECT '004', '1101',  DATE '2021-12-04' FROM DUAL UNION ALL
  SELECT '005', '1101',  DATE '2021-12-05' FROM DUAL UNION ALL
  SELECT '006', '1101',  DATE '2021-12-08' FROM DUAL UNION ALL
  SELECT '007', '1101',  DATE '2021-01-17' FROM DUAL UNION ALL
  SELECT '008', '1101',  DATE '2021-05-01' FROM DUAL UNION ALL
  SELECT '009', '1101',  DATE '2021-05-04' FROM DUAL UNION ALL
  SELECT '010', '1102',  DATE '2021-03-02' FROM DUAL UNION ALL
  SELECT '011', '1102',  DATE '2021-03-08' FROM DUAL UNION ALL
  SELECT '012', '1102',  DATE '2021-04-01' FROM DUAL UNION ALL
  SELECT '013', '1102',  DATE '2021-04-02' FROM DUAL UNION ALL
  SELECT '014', '1102',  DATE '2021-04-12' FROM DUAL UNION ALL
  SELECT '015', '1102',  DATE '2021-04-29' FROM DUAL UNION ALL
  SELECT '016', '1102',  DATE '2021-06-10' FROM DUAL UNION ALL
  SELECT '017', '1102',  DATE '2021-06-12' FROM DUAL;

Outputs:

CUSTOMER_ID	TRANS_DATE	GRP	TRANS_ID
1101	2020-11-02 00:00:00	1	001
1101	2020-11-14 00:00:00	1	002
1101	2020-11-18 00:00:00	1	003
1101	2021-01-17 00:00:00	2	007
1101	2021-05-01 00:00:00	3	008
1101	2021-05-04 00:00:00	3	009
1101	2021-12-04 00:00:00	4	004
1101	2021-12-05 00:00:00	4	005
1101	2021-12-08 00:00:00	4	006
1102	2021-03-02 00:00:00	1	010
1102	2021-03-08 00:00:00	1	011
1102	2021-04-01 00:00:00	1	012
1102	2021-04-02 00:00:00	2	013
1102	2021-04-12 00:00:00	2	014
1102	2021-04-29 00:00:00	2	015
1102	2021-06-10 00:00:00	3	016
1102	2021-06-12 00:00:00	3	017

fiddle