$this->db
->set(['in_population' => 1])
->where('email', $_SESSION['userid'])
->where('campaign', $_SESSION['campaign'])
->group_start()
->where('employee_title', $exclude_string)
->or_where('job_code', $exclude_string)
->or_where('department', $exclude_string)
->or_where('role', $exclude_string)
->group_end()
->update('employees');