Get rows without duplicate values

CREATE TABLE T1(a INT,b INT,c INT)

INSERT INTO T1(a,b,c)

SELECT 1,2,3

UNION

SELECT 2,2,4

UNION 

SELECT 3,3,3

UNION

SELECT 4,3,5

SELECT *

FROM T1

WHERE a NOT IN (SELECT MAX(a)

                FROM T1

                GROUP BY b)