MySQL server error report:Array ( [0] => Array ( [message] => MySQL Query Error ) [1] => Array ( [sql] => SELECT DISTINCT(b.goods_id) FROM `mwpa_cn`.`ecs_goods_attr` AS a, `mwpa_cn`.`ecs_goods_attr` AS b WHERE b.attr_value >= 57 AND b.attr_value <= AND b.attr_id = 20 ) [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 b.attr_id = 20' at line 1 ) [3] => Array ( [errno] => 1064 ) )