Mysql 如何从具有三个外键的多对多链接表中进行选择？？？描述中的图片

嘿，伙计们，我想学习如何从多对多数据库查询。这是一个包含三个表和一个带有三个外键的多对多表的数据库示例您将如何在

st\u glowne\u others

表上执行SELECT语句？

例如，如果我想从“st_components”表中选择所有可能的结果， 与“st_glowne”表中名称列中的特定值链接， 以及“st_pages”表中名称列的specyfic值。 提前谢谢

表1

CREATE TABLE `st_glowne` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `name` varchar(50) COLLATE utf8_polish_ci NOT NULL,
 `location` varchar(50) COLLATE utf8_polish_ci NOT NULL DEFAULT './',
 PRIMARY KEY (`name`),
 KEY `id` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8 COLLATE=utf8_polish_ci

表2

CREATE TABLE `st_pages` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `name` varchar(50) COLLATE utf8_polish_ci NOT NULL,
 `filelocation` varchar(50) COLLATE utf8_polish_ci NOT NULL DEFAULT 'pages/',
 PRIMARY KEY (`name`),
 KEY `id` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=6 DEFAULT CHARSET=utf8 COLLATE=utf8_polish_c

表3

CREATE TABLE `st_components` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `name` varchar(50) COLLATE utf8_polish_ci NOT NULL,
 `location` varchar(100) COLLATE utf8_polish_ci NOT NULL DEFAULT 'components/',
 PRIMARY KEY (`name`),
 KEY `id` (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 COLLATE=utf8_polish_ci

这是我们要从中查询的表：

CREATE TABLE `st_glowne_others` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `st_glowne` varchar(50) COLLATE utf8_polish_ci NOT NULL,
 `st_pages` varchar(50) COLLATE utf8_polish_ci NOT NULL,
 `st_components` varchar(50) COLLATE utf8_polish_ci NOT NULL,
 PRIMARY KEY (`id`),
 KEY `id` (`id`),
 KEY `st_glowne` (`st_glowne`),
 KEY `st_pages` (`st_pages`),
 KEY `st_components` (`st_components`),
 KEY `st_components_2` (`st_components`),
 CONSTRAINT `st_glowne_others_ibfk_3` FOREIGN KEY (`st_components`) REFERENCES `st_components` (`name`) ON DELETE CASCADE ON UPDATE CASCADE,
 CONSTRAINT `st_glowne_others_ibfk_1` FOREIGN KEY (`st_glowne`) REFERENCES `st_glowne` (`name`) ON DELETE CASCADE ON UPDATE CASCADE,
 CONSTRAINT `st_glowne_others_ibfk_2` FOREIGN KEY (`st_pages`) REFERENCES `st_pages` (`name`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_polish_ci

---

你能告诉我怎么查询吗？非常感谢

最简单的方法是使用连接：

SELECT * FROM `st_glowne_others` go
LEFT JOIN `st_glowne` ON `st_glowne`.name = go.st_glowne
LEFT JOIN `st_pages` ON `st_pages`.name = go.st_pages
LEFT JOIN `st_components` ON `st_components`.name = go.st_components

但是，我建议您重新考虑您的模式——PK作为名称字段有什么理由吗？您有一个

AUTO INCREMENT

id列，这是连接两个表的标准方法

例如（对于每个表格）：

然后使用

st_glowne_others

表，引用ID列

CREATE TABLE `st_glowne_others` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `st_glowne_id` int(11) NOT NULL,
 PRIMARY KEY (`id`),
 KEY `st_glowne_id` (`st_glowne_id`),
 CONSTRAINT `st_glowne_others_ibfk_3` FOREIGN KEY (`st_glowne_id`) REFERENCES `st_glowne` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
) 

CREATE TABLE `st_glowne_others` (
 `id` int(11) NOT NULL AUTO_INCREMENT,
 `st_glowne_id` int(11) NOT NULL,
 PRIMARY KEY (`id`),
 KEY `st_glowne_id` (`st_glowne_id`),
 CONSTRAINT `st_glowne_others_ibfk_3` FOREIGN KEY (`st_glowne_id`) REFERENCES `st_glowne` (`id`) ON DELETE CASCADE ON UPDATE CASCADE,
)