本文节选自《Netkiller Architect 手札》
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
CREATE DATABASE `sns` /*!40100 COLLATE 'utf8_general_ci' */
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
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;
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。
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