UPDATE t
SET t.Premium = (SELECT TOP 1 Max( t2.Premium )
FROM dbo.TableName t2
WHERE t2.SetId = 2012 AND t2.Id = t.ID)
FROM dbo.TableName t
WHERE t.SetId = 2013
UPDATE t
SET t.Premium = (SELECT TOP 1 Max( t2.Premium )
FROM dbo.TableName t2
WHERE t2.SetId = 2012 AND t2.Id = t.ID)
FROM dbo.TableName t
WHERE t.SetId = 2013