sql GROUP_CONCAT(... SEPARATOR) 简单

SELECT post.ID, post.User_id, post.Title, GROUP_CONCAT( tag.Tag_value
SEPARATOR ';' ) AS tags
FROM post
RIGHT JOIN tags_con_id ON tags_con_id.Post_ID = post.ID
LEFT JOIN tag ON tag.Tag_id = tags_con_id.Tag_id
GROUP BY post.ID
LIMIT 0 , 30 




--
-- 表的结构 `post`
--

CREATE TABLE `post` (
  `ID` int(11) NOT NULL,
  `Title` varchar(20) NOT NULL,
  `User_id` varchar(20) NOT NULL,
  `data` varchar(20) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

--
-- 导出表中的数据 `post`
--

INSERT INTO `post` (`ID`, `Title`, `User_id`, `data`) VALUES
(1, 'title1', '1', '2012-10-25'),
(2, 'test2', '1', '2012-10-25');

-- --------------------------------------------------------

--
-- 表的结构 `tag`
--

CREATE TABLE `tag` (
  `Tag_id` int(11) NOT NULL,
  `Tag_value` varchar(20) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;
--
-- 导出表中的数据 `tag`
--
INSERT INTO `tag` (`Tag_id`, `Tag_value`) VALUES
(1, 'Tag1'),
(2, 'Tag2'),
(3, 'Tag3'),
(4, 'Tag4'),
(5, 'Tag5'),
(6, 'Tag6'),
(7, 'Tag7'),
(8, 'Tag8');

-- --------------------------------------------------------

--
-- 表的结构 `tags_con_id`
--

CREATE TABLE `tags_con_id` (
  `ID` int(11) NOT NULL,
  `Post_ID` int(11) NOT NULL,
  `Tag_id` int(11) NOT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

--
-- 导出表中的数据 `tags_con_id`
--

INSERT INTO `tags_con_id` (`ID`, `Post_ID`, `Tag_id`) VALUES
(1, 1, 1),
(2, 1, 2),
(3, 1, 3),
(4, 2, 4),
(5, 2, 5),
(6, 2, 6),
(7, 2, 7);