using or_where() on same field

[eluser]blorriman[/eluser]
I'm not sure why, but by putting the or_where() before the where() seems to work.

Code:

$this->db->where('groups_members.group_id', $this->session->userdata('group_id'));
$this->db->where('groups_members.join_date <=', $end_date);
$this->db->or_where('groups_members.resign_date', NULL);
$this->db->where('groups_members.resign_date >=', $start_date);
$this->db->join('groups_members', 'groups_members.member_id = members.user_id');
$this->db->order_by('last_name', 'asc');
$query = $this->db->get('members');