数据表之间是纵横交叉、相互关联的,laravel的一对一,一对多比较好理解,官网介绍滴很详细了,在此我就不赘述啦,重点我记下多对多的关系
一种常见的关联关系是多对多,即表A的某条记录通过中间表C与表B的多条记录关联,反之亦然。比如一个用户有多种角色,反之一个角色对应多个用户。
为了测试该关联关系,我们沿用官网的用户角色示例:
需要三张数据表:users、roles 和 role_user,role_user 表按照关联模型名的字母顺序命名(这里role_user是中间表),并且包含 user_id 和 role_id两个列。
多对多关联通过编写返回 belongsToMany 方法返回结果的方法来定义。废话不说多,直接上数据结构:
1:创建一个角色表roles,并添加一些初始化数据:
SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure for users -- ---------------------------- DROP TABLE IF EXISTS `users`; CREATE TABLE `users` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) COLLATE utf8_unicode_ci NOT NULL, `email` varchar(255) COLLATE utf8_unicode_ci NOT NULL, `password` varchar(60) COLLATE utf8_unicode_ci NOT NULL, `remember_token` varchar(100) COLLATE utf8_unicode_ci DEFAULT NULL, `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00', `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00', PRIMARY KEY (`id`), UNIQUE KEY `users_email_unique` (`email`) USING BTREE ) ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; -- ---------------------------- -- Records of users -- ---------------------------- INSERT INTO `users` VALUES ('1', 'admin', 'admin@163.com', '$2y$10$J/yXqscucanrHAGZp9G6..Tu1Md.SOljX3M8WrHsUdrgat4zeSuhC', 'ilocXtjZJwhrmIdLG1cKOYegeCwQCkuyx1pYAOLuzY2PpScQFT5Ss7lBCi7i', '2016-04-21 16:26:23', '2016-12-14 09:29:59'); INSERT INTO `users` VALUES ('2', 'baidu', '10940370@qq.com', '$2y$10$2A5zJ4pnJ5uCp1DN3NX.5uj/Ap7P6O4nP2BaA55aFra8/rti1K6I2', null, '2016-04-22 06:48:10', '2016-04-22 06:48:10'); INSERT INTO `users` VALUES ('3', 'fantasy', '1009@qq.com', '', null, '2017-06-14 10:38:57', '2017-06-15 10:39:01');
2:创建一个角色表roles,并添加一些初始化数据:
SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure for roles -- ---------------------------- DROP TABLE IF EXISTS `roles`; CREATE TABLE `roles` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `name` varchar(255) COLLATE utf8_unicode_ci NOT NULL, `created_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00', `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci; -- ---------------------------- -- Records of roles -- ---------------------------- INSERT INTO `roles` VALUES ('1', '超级版主', '2016-04-21 16:26:23', '2016-12-14 09:29:59'); INSERT INTO `roles` VALUES ('2', '司令', '2016-04-22 06:48:10', '2016-04-22 06:48:10'); INSERT INTO `roles` VALUES ('3', '军长', '2017-06-14 10:38:57', '2017-06-15 10:39:01'); INSERT INTO `roles` VALUES ('4', '司长', '2017-06-07 10:41:41', '2017-06-15 10:41:51'); INSERT INTO `roles` VALUES ('5', '团战', '2017-06-22 10:41:44', '2017-06-28 10:41:54'); INSERT INTO `roles` VALUES ('6', '小兵', '2017-06-22 10:41:47', '2017-06-22 10:41:56');
3:创建一个中间表role_user用于记录users表与roles表的对应关系,并添加一些初始化数据:
SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure for role_user -- ---------------------------- DROP TABLE IF EXISTS `role_user`; CREATE TABLE `role_user` ( `id` int(10) unsigned NOT NULL AUTO_INCREMENT, `user_id` int(11) DEFAULT NULL, `role_id` int(11) DEFAULT NULL, `created_at` datetime DEFAULT NULL, `updated_at` datetime DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM AUTO_INCREMENT=8 DEFAULT CHARSET=latin1; -- ---------------------------- -- Records of role_user -- ---------------------------- INSERT INTO `role_user` VALUES ('1', '1', '2', '2017-06-07 11:42:13', '2017-06-21 11:32:16'); INSERT INTO `role_user` VALUES ('2', '1', '3', '2017-06-07 11:32:13', '2017-06-07 11:22:13'); INSERT INTO `role_user` VALUES ('3', '2', '4', '2017-06-07 11:32:13', '2017-06-07 11:12:13'); INSERT INTO `role_user` VALUES ('4', '1', '5', '2017-06-07 11:32:13', '2017-06-07 11:22:13'); INSERT INTO `role_user` VALUES ('5', '3', '6', '2017-06-07 11:32:13', '2017-06-07 11:52:13'); INSERT INTO `role_user` VALUES ('6', '3', '2', '2017-06-07 11:32:13', '2017-06-07 11:42:13'); INSERT INTO `role_user` VALUES ('7', '2', '2', '2017-06-07 11:42:13', '2017-06-07 11:52:13');
注意我们定义中间表的时候没有在结尾加s并且命名规则是按照字母表顺序,将role放在前面,user放在后面,并且用_分隔,这一切都是为了适应Eloquent模型关联的默认设置:在定义多对多关联的时候如果没有指定中间表,Eloquent默认的中间表使用这种规则拼接出来。
创建一个Role模型:
<?php namespace App\Models; use Illuminate\Database\Eloquent\Model; /** * Class Role * @package App\Models * @mixin \Eloquent */ class Role extends Model { }
然后我们在 User 模型上定义 roles 方法: