DECLARE @T1 TABLE
(
keycol INT NOT NULL,
C1 INT NULL,
C2 INT NULL,
C3 INT NULL,
C4 INT NULL,
C5 INT NULL
);
INSERT INTO @T1(keycol, C1, C2, C3, C4, C5) VALUES
(1, 17, NULL, 2, 5, NULL),
(2, 31, 59, NULL, 11, 13)
SELECT * FROM @T1
SELECT keycol,
(SELECT MAX(val) FROM (VALUES(C1),(C2),(C3),(C4),(C5)) AS D(val)) AS mx
FROM @T1;