fadsf, PostgreSQL - rextester

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DROP TABLE T;
CREATE TABLE T(ID int, Rank int, Event INT);

INSERT INTO T VALUES (123456, 1,'178');
INSERT INTO T VALUES (123456, 2,NULL);
INSERT INTO T VALUES (123456, 3,NULL);
INSERT INTO T VALUES (123456, 4,'155');
INSERT INTO T VALUES (123456, 5,NULL);
INSERT INTO T VALUES (123456, 6,'192');
INSERT INTO T VALUES (123456, 7,NULL);
INSERT INTO T VALUES (356589, 1,'165');
INSERT INTO T VALUES (356589, 2,NULL);
INSERT INTO T VALUES (356589, 3,NULL);
INSERT INTO T VALUES (356589, 4,NULL);
INSERT INTO T VALUES (565984, 1,'1025');
INSERT INTO T VALUES (565984, 2,NULL);
INSERT INTO T VALUES (987456, 1,'85');
INSERT INTO T VALUES (987456, 2,NULL);
INSERT INTO T VALUES (987456, 3,NULL);
INSERT INTO T VALUES (987456, 4,NULL);
INSERT INTO T VALUES (987456, 5,NULL);
INSERT INTO T VALUES (987456, 6,NULL);

WITH cte AS (
SELECT ID, RANK, EVENT, SUM(CASE WHEN event IS NULL THEN 0 ELSE 1 END) OVER(PARTITION BY ID ORDER BY RANK) AS grp
FROM t
)
SELECT ID, RANK, FIRST_VALUE(Event) OVER(PARTITION BY ID, grp  ORDER BY Rank) AS Event
FROM cte
ORDER BY ID, RANK


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