Cross-server data transfer is one of the more problematic areas of javascript in-browser programming today.
The obstacles are designed into the browser for good pragmatic security concerns, but sometimes you have legitimate need to retrieve data from multiple servers in one page.
Using Rdbhost databases from javascript applications is one such need, and we provide a library to make access easy and reliable. The method we recommend, the method our library supports, involves some domain name server (DNS) manipulation.
I assume you are hosting under your own domain name, and that your domain registrar provides a way to configure subdomains. Just create a subdomain of your domain that points at our server. The IP address of the Rdbhost server is on your profile page.
For example:
With that done, wait a few hours for the change to propagate across the internet.
Include the javascript module 'rdb.js' in your page, by reference, and create a javascript inline sequence to initialize an SQLEngine object. Here is a code sample, and line-by-line explanation follows
01 var uid = 'r0000000002';
02 var authcode = '2398473219847219834';
03 var rdb = new SQLEngine(uid,authcode,'rdbhost');
04 var query = 'SELECT * FROM css_data';
05 var res = rdb.query( {'callback' : success,
06 'q' : query } );
07 function success(json) {
08 // do something useful with data
09 for (var i=0; i<json.records.rows.length; i++) {
10 var val = json.records.rows[i];
11 alert('engine: '+val[0]);
12 }
13 }
Lines 01 and 02 just store the necessary user id and authcode, copied from the account_manager page.
Line 03 creates the SQLEngine object, which will handle making queries against the database.
Lines 04-06 query the database; the function
success is called with a data structure containing the retrieved records.
Lines 07-13 implement the callback
success, which simply loops over the list of rows, displaying an alert box with the value of the first field in each record.
Testing
The above script can be pasted into a script element in an html page, after a script element loading the rdb.js library, and (with a valid uid/authcode combo) will function. It does not need any supporting html, beyond the script container.
The jquery plugin
DataTables works very well with
Rdb.Js. See examples here:
JSON Example 1
JSON Example 2
The javascript database client code is inline in the source files, so
view-source will be informative.
API
The SQLEngine object has two methods intended for client use. The
query method, demonstrated above,
takes one object as a parameter, and expects at least two attributes in that object. See the documentation
page on site for more specifics.
The other method is
queryByForm, which takes three parameters: the first is a string with the id of
the source form, the second is the success callback function, and the last is an optional error callback. This method is useful if you wish to send file-sourced data to the server; you can put file-fields in your form, and after the user has selected files, the form can be submitted using the
queryByForm method. The form must have a field (hidden or otherwise)
q for the query, and optionally format, arg### and argtype### fields.
Rdb.js documentation
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