Postgres 9.3

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CREATE TABLE MY_TABLE (
    id VARCHAR(50),
    year VARCHAR(50)
);

INSERT INTO MY_TABLE (id, year) VALUES ('123', '2010');
INSERT INTO MY_TABLE (id, year) VALUES ('123', '2011');
INSERT INTO MY_TABLE (id, year) VALUES ('123', '2012');

INSERT INTO MY_TABLE (id, year) VALUES ('124', '2011');
INSERT INTO MY_TABLE (id, year) VALUES ('124', '2012');
INSERT INTO MY_TABLE (id, year) VALUES ('124', '2013');

INSERT INTO MY_TABLE (id, year) VALUES ('125', '2011');
INSERT INTO MY_TABLE (id, year) VALUES ('125', '2012');
INSERT INTO MY_TABLE (id, year) VALUES ('125', '2013');

INSERT INTO MY_TABLE (id, year) VALUES ('127', '2011');
INSERT INTO MY_TABLE (id, year) VALUES ('127', '2012');
INSERT INTO MY_TABLE (id, year) VALUES ('127', '2015');

INSERT INTO MY_TABLE (id, year) VALUES ('126', '2019');

WITH CTE AS (
  SELECT id, year, ROW_NUMBER() OVER (PARTITION BY id ORDER BY year) AS rn
  FROM MY_TABLE
),
CTE3 AS (
  select id
  , year
  , rn
  , max(rn) over (partition by id) as MaxRN
  from cte
),
CTE4 AS (  
  SELECT id
  , coalesce(max(CASE WHEN rn = 1 THEN year END), '') ||
    coalesce(max(CASE WHEN rn = 2  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 3  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 4  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 5  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 6  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 7  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 8  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 9  THEN ',' || year END), '') ||
    coalesce(max(CASE WHEN rn = 10 THEN ',' || year END), '')
    AS combination
  FROM CTE3
  GROUP BY id
)

SELECT combination
, count(id) as freq
FROM CTE4
GROUP BY combination

combination	freq
2011,2012,2015	1
2011,2012,2013	2
2010,2011,2012	1
2019	1

SELECT 4