mysql中GROUP_CONCAT的使用

現在有三個表，結構如下：

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

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 '分類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 '音頻，圖片之類',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COMMENT='附件表';

三張表數據如下：

cate表:

 article表:

 article_extend表:

問題來了，現在通過表連接查詢，查詢文章id為1的文章數據，並顯示文章標題，文章分類，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;

結果如下，出現了兩條數據：

現在只想要一條結果，aname字段進行合並，如何做？

只有通過 GROUP_CONCAT來實現了：

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;

結果如下：

那么，現在我們不想通過文章id一條一條的查，我們要取全部，但如果文章name有多個的要進行合並，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;

結果如下：