public function buildCondition(PlFilter $uf) { $sub = $uf->addNewsLetterFilter($this->nlid); $cond = $sub . '.nlid IS NOT NULL'; if (!is_null($this->issue_id)) { $cond = XDB::format($cond . ' AND ( ' . $sub . '.last IS NULL OR ' . $sub . '.last < {?})', $this->issue_id); } return $cond; }