[MySQL] Problema PROCEDURE

[zacca94]

Perchè questo non va:

DROP PROCEDURE `a`;
DELIMITER $
CREATE PROCEDURE `a`(in `b` int)    
BEGIN
        PREPARE `stmt` FROM 'select ?;';        
        EXECUTE `stmt` USING b;        
        DEALLOCATE PREPARE `stmt`;    
END$
DELIMITER ;
call a(1); 

e questo si:

DROP PROCEDURE `a`;
DELIMITER $
CREATE PROCEDURE `a`(in `b` int)    
BEGIN
        PREPARE `stmt` FROM 'select ?;';
        set @c = b;        
        EXECUTE `stmt` USING @c;        
        DEALLOCATE PREPARE `stmt`;    
END$
DELIMITER ;
call a(1); 

???

Grazie