mayores.sql

CREATE TABLE tabla_loca(
  id int PRIMARY KEY AUTO_INCREMENT,
  a int,
  b int
);

INSERT INTO tabla_loca (a, b) VALUES
(1, 3), 
(2, 1), 
(1, 5), 
(3, 2), 
(2, 3), 
(2, 6);

DELIMITER $$ 
CREATE PROCEDURE `seleccionar_mayores`() 
BEGIN
    SELECT a, max(b) FROM tabla_loca GROUP BY a;
END 
$$

CALL seleccionar_mayores();