SNS 数据库设计 - 码农教程

本文节选自《Netkiller Architect 手札》

4.21. SNS 数据库设计

这里讲解SNS交友社区的数据库设计与实现

我们要实现下面几个功能

朋友之间的关系，多对多关系
朋友之间的维度，如3度4度....
朋友的查找

		CREATE DATABASE `sns` /*!40100 COLLATE 'utf8_general_ci' */

4.21.1. people 表

people 是存储人，你可以用为user,member都可以

			CREATE TABLE `people` (
	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`name` VARCHAR(50) NOT NULL,
	PRIMARY KEY (`id`)
)
COMMENT='Social Network Site - Six Degrees of Separation - http://www.netkiller.cn'
COLLATE='utf8_general_ci'
ENGINE=InnoDB;

存储具体的这人

4.21.2. firend 表

这个表的功能主要是维持朋友之间的关系网，这里使用了多对多方式并且使用外键防止产生脏数据。

			CREATE TABLE `friend` (
	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`people_id` INT(10) UNSIGNED NOT NULL,
	`friend_id` INT(10) UNSIGNED NOT NULL,
	`ctime` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
	PRIMARY KEY (`id`),
	UNIQUE INDEX `unique` (`people_id`, `friend_id`),
	INDEX `FK_firend_people` (`people_id`),
	INDEX `FK_firend_people_2` (`friend_id`),
	CONSTRAINT `FK_firend_people` FOREIGN KEY (`people_id`) REFERENCES `people` (`id`),
	CONSTRAINT `FK_firend_people_2` FOREIGN KEY (`friend_id`) REFERENCES `people` (`id`)
)
COMMENT='Social Network Site - Six Degrees of Separation - http://www.netkiller.cn'
COLLATE='utf8_general_ci'
ENGINE=InnoDB;

4.21.3. 演示

首先初始化用户数据

			INSERT INTO `people` (`id`, `name`) VALUES
	(1, 'Neo'),
	(2, 'Luke'),
	(3, 'Jack'),
	(4, 'Joey'),
	(5, 'Jam'),
	(6, 'John');

建立朋友之间的关系

			INSERT INTO `friend` (`id`, `people_id`, `friend_id`) VALUES
	(1, 1, 2),
	(2, 1, 3),
	(3, 1, 4),
	(4, 1, 5),
	(5, 1, 6),
	(6, 2, 1),
	(7, 2, 3);

现在就可以查找你的朋友了

			select people.* from friend, people where friend.people_id = 1 and friend.friend_id = people.id;

查找朋友的朋友就比较麻烦了，必须使用递归方法，一层一层查下去，反复执行SQL效率是很低的，所以我们准备了第三张表。

4.21.4. network 表

关系网表，主要功能是弥补firend表，用于快速检索（在不使用递归的情况下）

			CREATE TABLE `network` (
	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`people_id` INT(10) UNSIGNED NOT NULL,
	`following_id` INT(10) UNSIGNED NOT NULL,
	`friend_id` INT(10) UNSIGNED NULL DEFAULT NULL,
	`degrees` VARCHAR(250) NOT NULL,
	`ctime` TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
	PRIMARY KEY (`id`),
	UNIQUE INDEX `unique` (`people_id`, `friend_id`, `following_id`),
	INDEX `FK_firend_people` (`people_id`),
	INDEX `FK_firend_people_2` (`friend_id`),
	INDEX `FK_friend_people_following_id` (`following_id`),
	CONSTRAINT `FK_firend_people` FOREIGN KEY (`people_id`) REFERENCES `people` (`id`),
	CONSTRAINT `FK_friend_people_following_id` FOREIGN KEY (`following_id`) REFERENCES `people` (`id`),
	CONSTRAINT `FK_friend_people_friend_id` FOREIGN KEY (`friend_id`) REFERENCES `people` (`id`)
)
COMMENT='Social Network Site - Six Degrees of Separation - http://www.netkiller.cn'
COLLATE='utf8_general_ci'
ENGINE=InnoDB;

following 一个朋友, Neo following Jam

			INSERT INTO `people` (`id`, `name`) VALUES
	(1, 'Neo'),
	(2, 'Luke'),
	(3, 'Jack'),
	(4, 'Joey'),
	(5, 'Jam'),
	(6, 'John');

INSERT INTO `network` (`people_id`, `following_id`, `friend_id`, `degrees`) VALUES ( 1, 5, NULL, '1.5');

之前Neo已经 following Jam，接下来查找Jam的朋友，现在Neo following John, John 是 Jam 的朋友，friend_id = NULL 表示 Jam 尚未有朋友

			select * from network where people_id=1 and friend_id = 5;

INSERT INTO `sns`.`network` (`people_id`, `following_id`, `friend_id`, `degrees`) VALUES ('1', '6', '5', '1.5.6');

Neo following Joey, Joey 是 Luke 的朋友，所以 Luke可能是 Neo的朋友

			INSERT INTO `sns`.`network` (`people_id`, `following_id`, `friend_id`, `degrees`) VALUES ('1', '4', '2', '1.2.4');

查询不同维度下的所有好友，查询出的用户ID需要处理。

			select * from network where people_id=1 and degrees like "1.%";
select * from network where people_id=1 and degrees like "1.2%";
select * from network where people_id=1 and degrees like "1.2.%";

至此社区管理网就建立起来了

上面的例子演示了 people_id=1 即 Neo 的关系网