Select every alternate days for selecting bus journey direction - php

Question

I am working on a bus ticket reservation systems . In this,I have made tables for all the routes and within the table I have added fields like bus_number,fare etc . Now our buses travels every alternate days in vice versa direction,ie if a bus travels from X->Y on 21-12-2011,the the same bus will travel Y->X on next date . So how am going to get the direction for a bus ? If I made tables for each bus service provider and add bus numbers add a identifier like 'to' for a date , I think it will be possible to to know the status for all next days . I dont know if its a good idea , so please help me.

Answer 1

Without knowing the precise details of your existing tables it is a little difficult to provide a definitive solution. Anyway, here's a suggestion of how you could hold buses along with their stops and fares:
CREATE TABLE `bus` (
`id` int unsigned not null primary key auto_increment,
`bus_number` varchar(55) not null,
UNIQUE KEY `busUidx1` (`bus_number`)
) ENGINE=InnoDB;
CREATE TABLE `bus_stop` (
`id` int unsigned not null primary key auto_increment,
`stop_description` varchar(250) not null,
UNIQUE KEY `bus_stopUidx1` (`stop_description`)
) ENGINE=InnoDB;
CREATE TABLE `bus_route` (
`id` int unsigned not null primary key auto_increment,
`bus_id` int unsigned not null,
`route_date` date not null,
`bus_start_stop_id` int unsigned not null,
`bus_end_stop_id` int unsigned not null,
`fare` decimal (10,2) not null,
UNIQUE KEY `bus_stopUidx1` (`bus_id`,`route_date`),
CONSTRAINT `fk_bus_route_bus_fk1` FOREIGN KEY (`bus_id`) REFERENCES `bus` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT `fk_bus_route_stop_fk1` FOREIGN KEY (`bus_start_stop_id`) REFERENCES `bus_stop` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
CONSTRAINT `fk_bus_route_stop_fk2` FOREIGN KEY (`bus_end_stop_id`) REFERENCES `bus_stop` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION
) ENGINE=InnoDB;
Using this model you should be able to store a list of buses (in the bus table), a list of all possible stops (in the bus_stop table) and bus routes for a given date. It will also allow you the flexibility to break the 'bus travels from X > Y and then always travels back from Y > X' rule which, if the buses that I have travelled on in the past are anything to go by, might prove useful ;-)
EDIT
So here is some sample data to try and illustrate my answer further:
insert into bus (bus_number) values ('Red Bus 1');
insert into bus (bus_number) values ('Red Bus 2');
insert into bus (bus_number) values ('Yellow Bus 1');
insert into bus (bus_number) values ('Yellow Bus 2');
insert into bus_stop (stop_description) values ('Stop 1');
insert into bus_stop (stop_description) values ('Stop 2');
insert into bus_stop (stop_description) values ('Stop 3');
insert into bus_stop (stop_description) values ('Stop 4');
insert into bus_route (bus_id,route_date,bus_start_stop_id,bus_end_stop_id,fare)
values (
(select id from bus where bus_number = 'Red Bus 1'),
'2011-12-11',
(select id from bus_stop where stop_description = 'Stop 1'),
(select id from bus_stop where stop_description = 'Stop 2'),
3.45);
insert into bus_route (bus_id,route_date,bus_start_stop_id,bus_end_stop_id,fare)
values (
(select id from bus where bus_number = 'Red Bus 1'),
'2011-12-12',
(select id from bus_stop where stop_description = 'Stop 2'),
(select id from bus_stop where stop_description = 'Stop 1'),
3.45);
insert into bus_route (bus_id,route_date,bus_start_stop_id,bus_end_stop_id,fare)
values (
(select id from bus where bus_number = 'Yellow Bus 1'),
'2011-12-11',
(select id from bus_stop where stop_description = 'Stop 3'),
(select id from bus_stop where stop_description = 'Stop 4'),
1.95);
insert into bus_route (bus_id,route_date,bus_start_stop_id,bus_end_stop_id,fare)
values (
(select id from bus where bus_number = 'Yellow Bus 1'),
'2011-12-12',
(select id from bus_stop where stop_description = 'Stop 4'),
(select id from bus_stop where stop_description = 'Stop 3'),
1.95);
And finally a query to join the tables together:
select b.bus_number,
br.route_date,
bs.stop_description as start,
be.stop_description as end,
br.fare
from bus_route br
inner join bus b on b.id = br.bus_id
inner join bus_stop bs on bs.id = br.bus_start_stop_id
inner join bus_stop be on be.id = br.bus_end_stop_id;