yii\db\Query::union PHP Méthode

    public function union($sql, $all = false)
    {
        $this->union[] = ['query' => $sql, 'all' => $all];
        return $this;
    }

 protected function _prepareQuery()
 {
     if (!$this->_query_string) {
         throw new \Exception("Error query string cannot be empty");
     }
     $q = $this->_query_string;
     $queryArticle = new Query();
     $queryArticle->select('name, preview_text, seourl, image')->from('article')->where(['like', 'name', $q])->orWhere(['like', 'preview_text', $q])->orWhere(['like', 'detail_text', $q])->orWhere(['like', 'soc_text', $q])->orWhere(['like', 'title', $q])->limit(10);
     $queryStructure = new Query();
     $queryStructure->select('label AS name, description AS preview_text, seourl, image')->from('structure')->where(['is_dir' => 0])->andWhere(['or', ['like', 'label', $q], ['like', 'content', $q], ['like', 'info', $q], ['like', 'title', $q]])->limit(10);
     $queryArticle->union($queryStructure);
     return $queryArticle;
 }