亲宝软件园·资讯

展开

mysql GROUP_CONCAT使用方法 mysql中GROUP_CONCAT如何使用实例分析

怀素真 人气:0

本文实例讲述了mysql中GROUP_CONCAT的使用方法。分享给大家供大家参考,具体如下:

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:

希望本文所述对大家MySQL数据库计有所帮助。

加载全部内容

相关教程
猜你喜欢
用户评论