Massive update with where statement on sql

DECLARE @CHANGES  AS TABLE (
	OLDVALUE INT
	,NEWVALUE INT
);

DECLARE @MAINTABLE AS TABLE(
	ID INT
	,NUM INT
);

INSERT INTO @CHANGES VALUES (1,100);
INSERT INTO @CHANGES VALUES (2,3000);
INSERT INTO @CHANGES VALUES (3,417);
INSERT INTO @CHANGES VALUES (4,85);
INSERT INTO @CHANGES VALUES (5,662);
INSERT INTO @CHANGES  VALUES (6,995);


INSERT INTO @MAINTABLE VALUES (1,1);
INSERT INTO @MAINTABLE VALUES (2,1);
INSERT INTO @MAINTABLE VALUES (3,2);
INSERT INTO @MAINTABLE VALUES (4,3);
INSERT INTO @MAINTABLE VALUES (5,3);
INSERT INTO @MAINTABLE VALUES (6,3);
INSERT INTO @MAINTABLE VALUES (7,3);
INSERT INTO @MAINTABLE VALUES (8,3);
INSERT INTO @MAINTABLE VALUES (9,4);
INSERT INTO @MAINTABLE VALUES (10,5);
INSERT INTO @MAINTABLE VALUES (11,6);
INSERT INTO @MAINTABLE VALUES (12,6);
INSERT INTO @MAINTABLE VALUES (13,6);

--SELECT * FROM @CHANGES;
SELECT * FROM @MAINTABLE;

UPDATE M SET M.NUM = C.NEWVALUE
FROM @MAINTABLE AS M 
	INNER JOIN @CHANGES AS C ON M.NUM = C.OLDVALUE

SELECT * FROM @MAINTABLE;

declare cur cursor for select oldVal,newVal from changeVals

declare @OldVal int
declare @NewVal int

OPEN cur
FETCH NEXT FROM cur INTO @OldVal, @NewVal 

WHILE @@FETCH_STATUS = 0
BEGIN
        update table set column = @NewVal where column = @OldVal
        FETCH NEXT FROM cur INTO @OldVal, @NewVal 
END

CLOSE cur
DEALLOCATE cur