能否一次查询取出各栏目记录的总数,该怎么处理

Create Table

CREATE TABLE `demo` (
  `demoId` int(11) NOT NULL AUTO_INCREMENT,
  `class_id` int(11) DEFAULT NULL,
  PRIMARY KEY (`demoId`)
) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=utf8
//2 录入测试数据

//3 查询
SELECT COUNT(class_id),class_id FROM demo GROUP BY class_id