execution plan

create schema mydb ;
use mydb;
CREATE TABLE bill_range (
    id int(11) NOT NULL AUTO_INCREMENT,
    low varchar(255) NOT NULL,
    high varchar(255) NOT NULL,
    PRIMARY KEY (id),
    bill_id int(11) NOT NULL,
    FOREIGN KEY (bill_id) REFERENCES bill(id)
);
CREATE TABLE bill (
    id int(11) NOT NULL AUTO_INCREMENT,
    label varchar(10),
    PRIMARY KEY (id)
);
create index bill_range_low_high_index on bill_range( low, high);

show index from bill_range from mydb;
insert into bill (label) values('a');
insert into bill (label) values('b');
insert into bill (label) values('c');
insert into bill (label) values('d');

insert into bill_range (low,high,bill_id) values(1000,2000,1);
insert into bill_range (low,high,bill_id) values(2001,3000,2);
insert into bill_range (low,high,bill_id) values(3001,4000,2);
insert into bill_range (low,high,bill_id) values(4001,5000,3);
insert into bill_range (low,high,bill_id) values(5001,6000,3);
insert into bill_range (low,high,bill_id) values(6001,7000,2);
insert into bill_range (low,high,bill_id) values(7001,8000,4);
insert into bill_range (low,high,bill_id) values(8001,9000,1);
insert into bill_range (low,high,bill_id) values(9001,9999,2);

commit;