dynamic dependent select box with one table

[sonofjorel]

I have a table in a database that I need to filter upon using dependent select boxes.  The database was poorly designed and would be difficult to break into separate tables without affecting code written in other places.  I have found some good code and understanding of how to implement the dependent select boxes if you have two tables with one column functioning as a lookup value between the two.

 

I have provided a short bit of sql of what the table looks like with some column names changed.  I would need to first sort by lastname and have firstname dependent on the selection of lastname.  Any help would be greatly appreciated.

 

create table `user` (
`id` int(3) Not Null Auto_increment,
`firstname` varchar (60),
`lastname` varchar (24),
`age` double ,
`hometown` varchar (75),
`job` varchar (75),
`birthdate` date 
); 
insert into `user` (`id`, `firstname`, `lastname`, `age`, `hometown`, `job`, `birthdate`) values
('1','Peter','Griffin','41','Quahog','Brewery','1960-01-01'),
('2','Lois','Griffin','40','Newport','Piano Teacher','1961-08-11'),
('3','Joseph','Swanson','39','Quahog','Police Officer','1962-07-23'),
('4','Glenn','Quagmire','41','Quahog','Pilot','1960-02-28'),
('5','Megan','Griffin','16','Quahog','Student','1984-04-24'),
('6','Stewie','Griffin','2','Quahog','Dictator','2008-03-03');

[webbhelp]

How do you mean by have firstname dependent on lastname?

[sonofjorel]

after lastname is selected, then the first names associated with that name are present in the firstname select box.  i.e. if Griffin is chosen as a last name, then only peter, lois, megan and stewie are selectable in the firstname select box

[webbhelp]

Do you mean have to do that?

Use AJAX,

 

And send the chosen name to the php file which is Selecting, the firstnames and put it into a select box

[sonofjorel]

there in lies my problem.  I understand what technologies are involved with this, I am just unclear how to go about using php and AJAX with one table to filter out the results.  If I could use two tables as shown below, I would not have an issue.

 

Thanks

 

create table `lname` (
   `id` int(3) Not Null Auto_increment,
   `lastname` varchar (24)
);
insert into `lname` (`id`, `lastname`) values
('1', 'Griffin'),
('2', 'Quagmire'),
('3', 'Swanson');

create table `fname` (
   `id` int(3) Not Null,
   `firstname` varchar (60)
);

insert into `fname` (`id`, `firstname`) values
('1','Peter'),
('1','Lois'),
('3','Joseph'),
('2','Glenn'),
('1','Megan'),
('1','Stewie');