Multiple databases

I am using 1.9.4 with serverside database access.

$query = "SELECT ccCubeCart_customer.customer_id, status, cart_order_id, time, title, firstName, lastName, ccCubeCart_order_sum.campaign, ccCubeCart_customer.country, postcode_d, country_d, noOrders, language, comments_customers, ip, prod_total, shipMethod, tracking_no, gateway, comments, shipMethod_code,  ccCubeCart_customer.email FROM ccCubeCart_order_sum INNER JOIN ccCubeCart_customer ORDER BY time DESC";
$results = $db->select($query);

how to add this to the example from:

http://datatables.net/release-datatables/examples/data_sources/server_side.html

???
The data will be taken from three databases!

$aColumns = array( '????' );

/* Indexed column (used for fast and accurate table cardinality) */
$sIndexColumn = "cart_order_id";

/* DB table to use */
$sTable = "ccCubeCart_order_sum";

$sWhere = "";

Greetings Michel