A popular workaround to avoid browser caching of XHR requests is to add a bogus parameter to the request.
The javascript Date object is useful as it'll always return a unique bogus parameter.
A typical request that will avoid browser caching is:
var requestUrl='http://my.server.com?key=value&bogus_param='+new Date().getTime();
That javascript will ensure that every requestUrl contains a unique bogus_param value and avoid browser caching.
You could do something very similar in your B4A code.
From the code that you posted it looks like your B4A is querying a PHP script, so another solution is to set a header in the output of the PHP script to disable caching:
header('Cache-Control: no-cache, must-revalidate');
Note that the PHP header statement must be executed before any text or other output is output by the script - put that header statement at the very start of your PHP script otherwise you'll get an error such as 'headers already sent'.
Disabling caching in the SQL server is a bad idea - it's more likely that the request is being cached elsewhere and your SQL server is not even being re-queried.
Even so disabling SQL server caching could cause major loss of performance.
Martin.