PROBLEM:
I needed to add a NOT IN condition with a nested query for the WHERE condition. The usual method wont work
$view->query->where[1]['conditions'][] = array(
['field'] => 'groups_group_membership.type'
['value'] => array
(
[0] => 'SELECT_QUERY_HERE'
)['operator'] => IN
);
SOLUTION :
The way that works
/**
* Implementation of hook_views_query_alter
* @param type $view
* @param type $query
*/
function your_module_views_query_alter(&$view, &$query) {
if ($view->name == 'your_view' && $view->current_display == 'your_display') {$view->query->where[1]['conditions'][] = array(
'field' => 'your_field' NOT IN (SELECT gm.uid from group_membership gm where gm.gid=groups_group_membership_parent_groups.gid)',
'value' => array(),
'operator' => 'formula'
);
}
}