MySQL server error report:Array ( [0] => Array ( [message] => MySQL Query Error ) [1] => Array ( [sql] => SELECT c.cat_id, c.cat_name, c.sort_order, a.article_id, a.title, a.file_url, a.open_type FROM `07_ruixiang`.`rx_article` AS a LEFT JOIN `07_ruixiang`.`rx_article_cat` AS c ON a.cat_id = c.cat_id WHERE c.cat_type = AND a.is_open = 1 ORDER BY c.sort_order ASC, a.article_id ) [2] => Array ( [error] => You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'AND a.is_open = 1 ORDER BY c.sort_order ASC, a.article_id' at line 1 ) [3] => Array ( [errno] => 1064 ) )