This is one way. There are perhaps other ways that utilize the MIN function:;WITH cte AS
(
SELECT GAMt1, GAMt2,
ROW_NUMBER() OVER (PARTITION BY ID ORDER BY Datt) AS RN
FROM
YourTable
)
UPDATE cte SET
GAMt1 = 0,
GAMt2 = 0
WHERE
RN > 1;
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-- Yes, I am indeed a fictional character.