[1064 You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '=) 
                GROUP BY acc_index_id
                ORDER BY acc_catego...' at line 4 
 SELECT 
                GROUP_CONCAT(acc_category_id SEPARATOR ',') as categories_ids
                FROM `ep_material_category_tree` 
                WHERE acc_index_id IN (OGFraGZGOXVMa3NVUTZzd1FEa2lkejd5WkdGNElhRXdOamNrZkU3cA==) 
                GROUP BY acc_index_id
                ORDER BY acc_category_rank DESC]