mysql中GROUP_CONCAT的使用

现在有三个表，结构如下：

cate表
CREATE TABLE `cate` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT 'id',
  `name` char(20) DEFAULT '' COMMENT '分类名',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8 COMMENT='文章分类表';

article表
CREATE TABLE `article` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT COMMENT 'id',
  `title` varchar(50) DEFAULT '',
  `cate_id` int(11) NOT NULL DEFAULT '0' COMMENT '分类id',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8 COMMENT='文章表';

article_extend表
CREATE TABLE `article_extend` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `article_id` int(10) unsigned DEFAULT '0' COMMENT '文章id',
  `name` varchar(255) DEFAULT '' COMMENT '音频，图片之类',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COMMENT='附件表';

三张表数据如下：

cate表:

article表:

article_extend表:

问题来了，现在通过表连接查询，查询文章id为1的文章数据，并显示文章标题，文章分类，文章name。

SELECT
	a.id AS aid,
	a.title AS atitle,
	c. NAME AS cname,
	ae. NAME AS aname
FROM
	article AS a
LEFT JOIN cate AS c ON a.cate_id = c.id
LEFT JOIN article_extend AS ae ON a.id = ae.article_id
WHERE
	a.id = 1;

结果如下，出现了两条数据：

现在只想要一条结果，aname字段进行合并，如何做？

只有通过GROUP_CONCAT来实现了：

SELECT
	a.id AS aid,
	a.title AS atitle,
	c. NAME AS cname,
	GROUP_CONCAT(ae. NAME SEPARATOR '-') AS aname
FROM
	article AS a
LEFT JOIN cate AS c ON a.cate_id = c.id
LEFT JOIN article_extend AS ae ON a.id = ae.article_id
WHERE
	a.id = 1;

结果如下：

那么，现在我们不想通过文章id一条一条的查，我们要取全部，但如果文章name有多个的要进行合并，如何做？

SELECT
	a.id AS aid,
	a.title AS atitle,
	c. NAME AS cname,
	ae.allname
FROM
	article AS a
LEFT JOIN (
	SELECT
		ae.article_id,
		GROUP_CONCAT(ae. NAME) AS allname
	FROM
		article_extend AS ae
	GROUP BY
		ae.article_id
) AS ae ON a.id = ae.article_id
LEFT JOIN cate AS c ON a.cate_id = c.id;

结果如下：