WITH
n AS (
  SELECT
    [m1] = 1,
    [m2] = 2,
    [m3] = 3,
    [mn] = 1024
)
SELECT 
  SUM( ss.[m] ) 
FROM 
  n
  CROSS APPLY (
    VALUES ( [m1] ), ( [m2] ), ( [m3] ), ( [mn] )
  ) ss ( [m] )
HAVING
  SUM( ss.[m] ) >= 42
;
WITH
n AS (
  SELECT
    [m1] = 1,
    [m2] = 2,
    [m3] = 3,
    [mn] = 1024
)
SELECT 
  SUM( [m] )
FROM 
  n
  UNPIVOT (
    [m] FOR X
    IN ( [m1], [m2], [m3], [mn] )
  ) ss
HAVING
  SUM( [m] ) >= 42
;