SO-37839480

DECLARE @table TABLE (Rate INT, MatID INT);

INSERT  INTO @table
        (Rate, MatID)
VALUES  (1, 81),
        (2, 82),
        (2, 83),
        (3, 85),
        (2, 86),
        (2, 87),
        (3, 88);

SELECT  Rate,
        MatID
FROM    @table;

;
WITH    CTE_MinMatID
          AS (
              SELECT    Rate,
                        MIN(MatID) MinMatID
              FROM      @table
              GROUP BY  Rate
             )
    UPDATE  t
    SET     t.MatID = cte.MinMatID
    FROM    @table AS t
    INNER JOIN CTE_MinMatID cte ON cte.Rate = t.Rate;

SELECT  Rate,
        MatID
FROM    @table;