SELECT post.ID, post.User_id, post.Title, GROUP_CONCAT( tag.Tag_valueSEPARATOR ';' ) AS tagsFROM postRIGHT JOIN tags_con_id ON tags_con_id.Post_ID = post.IDLEFT JOIN tag ON tag.Tag_id = tags_con_id.Tag_idGROUP BY post.IDLIMIT 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);