create table `regions`(
region_id int auto_increment,
region_name varchar(100),
primary key (region_id)
);
insert into `regions`(region_name)
values
('Europe'),
('Americas'),
('Asia'),
('Middle East and Africa');
select * from `regions`r1
JOIN regions r2 ON (r1.region_id = LENGTH(r2.region_id)/2);
;