Post and Tags Relation

db.sql

-- Adminer 3.2.2 MySQL dump

SET NAMES utf8;
SET foreign_key_checks = 0;
SET time_zone = 'SYSTEM';
SET sql_mode = 'NO_AUTO_VALUE_ON_ZERO';

DROP TABLE IF EXISTS `posts`;
CREATE TABLE `posts` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `title` varchar(300) NOT NULL,
  `content` text NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=utf8;

INSERT INTO `posts` (`id`, `title`, `content`) VALUES
(1,	'test 1',	'test 1'),
(2,	'test 2',	'test 2'),
(3,	'test 3',	'test 3'),
(4,	'test 4',	'test 4'),
(5,	'test 5',	'test 5'),
(6,	'test 6',	'test 6'),
(7,	'test 7',	'test 7');

DROP TABLE IF EXISTS `posts_tags`;
CREATE TABLE `posts_tags` (
  `post_id` int(11) NOT NULL,
  `tag_id` int(11) NOT NULL
) ENGINE=MyISAM DEFAULT CHARSET=utf8;

INSERT INTO `posts_tags` (`post_id`, `tag_id`) VALUES
(1,	1),
(1,	2),
(1,	3),
(2,	1),
(2,	4);

DROP TABLE IF EXISTS `tags`;
CREATE TABLE `tags` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(300) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=6 DEFAULT CHARSET=utf8;

INSERT INTO `tags` (`id`, `name`) VALUES
(1,	'tag1'),
(2,	'tag2'),
(3,	'tag3'),
(4,	'tag4'),
(5,	'tag5');

-- 2011-09-16 11:14:08

Query to select all tags in a single query with tags concatenated .

SELECT p.*, 
( SELECT GROUP_CONCAT(t.name) as tag_name 
    FROM posts_tags as pt, tags as t 
    WHERE pt.post_id = p.id 
        AND pt.tag_id = t.id  ) as tag_name
FROM posts as p WHERE p.id = 1

You can read over the blog post also http://poeticcode.wordpress.com/2007/05/29/mysql-string-concat-multiple-rows/