mysql group_concat 實(shí)現(xiàn)把分組字段寫(xiě)成一行的方法示例

CREATE TABLE `book_tag` (
 `id` int(10) NOT NULL AUTO_INCREMENT,
 `tag_name` varchar(255) NOT NULL DEFAULT '0' COMMENT '標(biāo)簽名稱',
 `tag_nums` int(10) NOT NULL DEFAULT '0' COMMENT '引用數(shù)量',
 PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

CREATE TABLE `book_tag_book` (
 `id` int(10) NOT NULL AUTO_INCREMENT,
 `book_id` int(10) NOT NULL DEFAULT '0' COMMENT '書(shū)本id',
 `tag_id` int(10) NOT NULL DEFAULT '0' COMMENT '標(biāo)簽ID',
 PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

SELECT
 `b`.`id`,
 `b`.`book_name`,
 `b`.`book_flash`,
 `b`.`introduction`,
 GROUP_CONCAT(a.tag_name)
FROM
 `book_book` `b`
LEFT JOIN `book_tag_book` `t` ON `t`.`book_id` = `b`.`id`
LEFT JOIN `book_tag` `a` ON `a`.`id` = `t`.`tag_id`
GROUP BY b.id