CREATE TABLE `a_table` (
  `a_id` int(11) DEFAULT NULL,
  `a_name` varchar(10) DEFAULT NULL,
  `a_part` varchar(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8

————————————————
CREATE TABLE `b_table` (
  `b_id` int(11) DEFAULT NULL,
  `b_name` varchar(10) DEFAULT NULL,
  `b_part` varchar(10) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8

select * from a_table a inner join b_table b on a.a_id = b.b_id;

select * from a_table a left join b_table b on a.a_id = b.b_id;

select * from a_table a right join b_table b on a.a_id = b.b_id;