How to code services in wordpress?

[youvi]

See am doing an android application,it has a web back end,am using wordpress,but how can i code web services in wordpress?suppose i need to fetch some contents from database and pass it as json to android phones.So where should i place the php script or how can i do this?Is it possible to do web services using wordpress?

Here is the code:

$select_qry="select * from admin_details where username='$uname' and  password='$paswd'";
$result=mysql_query($select_qry);
$rows=mysql_num_rows($result);
if($rows>0)
$admin_arr=mysql_fetch_assoc($result);
json_encode($admin_arr);

How can i do this in wordpress?

Please help me..

Thanks

[technoknol]

i think you can not do it,
because the database you are fetching is not on wordpress server, so register on any webhost and create here database then upload your php file on that server.