Microsoft SQL Server Streak Counter

Question

I have data in the following format:

ID	Period	Date
1	1	2020-09-05
1	2	2020-10-01
1	3	2020-10-30
2	2	2020-10-01
2	4	2020-12-05
2	6	2021-02-05
3	1	2020-09-05

I want to calculate a streak grouping by both ID and period. The first date instance for each group should start at one, and if the date in the next row is less than 30 days from the first row, +1 to the streak counter. This should reset to 1 if the next row is 30 or more days.

This is my desired output:

ID	Period	Date	Counter
1	1	2020-09-05	1
1	2	2020-10-01	2
1	3	2020-10-30	3
2	2	2020-10-01	1
2	4	2020-12-05	1
2	6	2021-02-05	1
3	1	2020-09-05	1

I'm completely stuck on this - any help would be greatly appreciated. I'm using Microsoft SQL server.

EDIT: Actually using Microsoft SQL Server

Answer 1

From Oracle 12c, you can use MATCH_RECOGNIZE to perform a row-by-row comparison:

SELECT id,
       period,
       "DATE",
       counter
FROM   table_name
MATCH_RECOGNIZE(
  PARTITION BY id
  ORDER     BY "DATE"
  MEASURES
    COUNT(*) AS counter
  ALL ROWS PER MATCH
  PATTERN (any_date streak_date*)
  DEFINE
    streak_date AS "DATE" <= PREV("DATE") + INTERVAL '30' DAY
              -- AND PREV(period) < period
)

Which, for the sample data:

CREATE TABLE table_name (ID, Period, "DATE") AS
SELECT 1, 1, DATE '2020-09-05' FROM DUAL UNION ALL
SELECT 1, 2, DATE '2020-10-01' FROM DUAL UNION ALL
SELECT 1, 3, DATE '2020-10-30' FROM DUAL UNION ALL
SELECT 2, 2, DATE '2020-10-01' FROM DUAL UNION ALL
SELECT 2, 4, DATE '2020-12-05' FROM DUAL UNION ALL
SELECT 2, 6, DATE '2021-02-05' FROM DUAL UNION ALL
SELECT 3, 1, DATE '2020-09-05' FROM DUAL

Note: DATE is a reserved word and it is bad practice to use it as a column name.

Outputs:

ID	PERIOD	DATE	COUNTER
1	1	2020-09-05 00:00:00	1
1	2	2020-10-01 00:00:00	2
1	3	2020-10-30 00:00:00	3
2	2	2020-10-01 00:00:00	1
2	4	2020-12-05 00:00:00	1
2	6	2021-02-05 00:00:00	1
3	1	2020-09-05 00:00:00	1

db<>fiddle here