Calling a Drupal module function from jquery ajax.

You can call a module function from the jquery ajax function to perform some database related operations based on ajax.
To start, create a menu item using hook_menu

function mymodule_menu() {

  $items = array();

  // Create a path to send our AJAX request to.
  $items['mymodule_ajax'] = array(
    'title' => 'menu title',
    'page callback' => 'mymodule_ajax_function',   
    'access arguments' => array('access example ajax'),
    'type' => MENU_CALLBACK,
  );

  return $items;
}

function mymodule_ajax_function(){
// Here you can perform your database operations
    $var = "testing";
    return drupal_json($var);
}

And then add a js file to your module and paste the following code.

Drupal.behaviors.mymodule=function(context){

//click event
jQuery.ajax({
url: "mymodule_ajax",
                        type: "POST",
dataType: "json",
                        success:  function(data){
alert(data);
}
                      });

}


Cheers

Changing the admin password using drush of a drupal site.

Here is the drush command for changing the admin password for the drupal admin user.

drush upwd admin --password=your_new_password

The admin will be the username of the user with user id 1.