[web2py] Dependent drop downs

[Neveen Adel]

Hello,

I have
db.define_table('type',
                SQLField('name','string',length=2)
                SQLField('parent','reference db.type')
)

db.define_table('member',
                SQLField('name','string'),
                SQLField('type',db.type),
                SQLField('subtype',db.type),
)

I want when select a value of type the drop down of subtype changed
according to selection.

when am searching on it i found a solution that someone posted it
before
"
$('#tourplan_city').change(function(){ $.ajax( ........ ) }
"
But i don't know what is the " $.ajax( ........ ) " and where i will
write my query that compute result of subtype dropdown?

Could anyone help me ?

Thanks in advance

Neveen