create table `z` (`a` int,`b` int,`c` int, primary key `a`);

insert into `z` values ( 1 , 1 , 1 ),( 2 , 1 , 3 ),( 3 , 2 , 5 ),( 4 , 2 , 1 ),( 5 , 2 , 20 ),( 6 , 2 , 30 ),( 7 , 2 , 29 ),( 8 , 1 , 29 ),( 9 , 3 , 1 );

select `x`.* from `z` as `x` left join `z` as `y` on ((`x`.`b` = `y`.`b`) and (`y`.`c` > `x`.`c`)) where `y`.`a` is null;

+---+------+------+
| a | b    | c    |
+---+------+------+
|  6  |     2  |    30  |
|  8  |     1  |    29  |
|  9  |     3  |     1  |
+---+------+------+
 3  rows in set ( 0 . 00  sec)