6

假设我有一个像这样的模式：

group
-----
id

site
----
id
group_id (optional)

person
------
id
group_id (one of these two must exist 
site_id   and the other must be null)

device
------
id 
group_id  (one of these three must exist 
site_id    and the others must be null)
person_id

我不喜欢这种表示，但我正在努力寻找更好的表示。

我想到的两种选择是：

device
------
id 
parent_table_name
parent_id

（但这很糟糕，因为我不能再有外键了）

和：

entity
------
id

group
-----
entity_id

site
----
entity_id
link_entity_id (optional)

person
------
entity_id
link_entity_id (optional)

device
------
entity_id
link_entity_id

这也不够完美。它实际上是 Django ORMs 的继承方法，其中 entity 是所有其他类的父类。

有没有更好的结构化数据的方法，或者 SQL 只是与 DAG 不一致？

有没有办法将CONSTRAINTs 添加到 person 和 device 表中？

4

3 回答 3

1

这是典型的类型/子类型情况。您的第二种选择更好，您可以更进一步。如果您更熟悉这些概念，请考虑 OO 编程。

这就是我对您的实体进行分类的方式。“抽象”实体在括号中。

             （所有者）设备
               |
         +-----------+
         | |
   （隶属）人
         |
     +-------+
     | |
   集团网站

下面是如何阅读它：

  • 所有者的类型是：个人或附属机构（我找不到更好的名称，抱歉）。一个人“是”所有者，而从属关系“是”所有者。
  • 隶属关系的类型是：组或站点
  • 一个人隶属于一个附属机构，一个团体或一个网站
  • 一个设备有一个所有者，一个组、一个站点或一个人

如何将其转换为表格：

能效比图

现在你可以坚持你的第一个选择。MySQL 不支持CHECK()声明任意约束的语法，但是通过使用触发器可以达到同样的效果，但是语法比较麻烦，性能值得怀疑。

于 2013-06-07T17:44:03.933 回答
1

以下 MySQL 结构应该正常化。它会使您的查询在某些情况下编写起来更加复杂，但它会使应用程序更强大，并且能够成倍增长而不会影响性能。我们有一个大型 MySQL 数据库，其中包含许多相关表，这些表为人们保存各种采访、笔记和其他非常棒的数据的外键！一个注意事项是，如果您使用 group 作为表名，请记住使用 `` 标记，例如：

`group`

这样 MySQL 就不会尝试使 aINNER JOIN group ON (foo=bar)和 expect无效GROUP BY。您还必须在应用程序的前端设置限制，以防止在没有父设备的情况下添加设备（如果这是所需的目标）。但这并不难做到。不管怎样，看看这些例子，享受有趣的实验/编程吧！

在线演示：http ://www.sqlfiddle.com/#!2/e9e94/2/0

这是建议的 MySQL 表结构，其中包含最少的数据，以说明您的问题中每个所需案例的一个实例：复制并粘贴到 .sql 文件并使用 phpMyAdmin 导入到空数据库

-- phpMyAdmin SQL Dump
-- version 3.5.2.2
-- http://www.phpmyadmin.net
--
-- Host: 127.0.0.1
-- Generation Time: Jun 07, 2013 at 08:14 PM
-- Server version: 5.5.27
-- PHP Version: 5.4.7

SET FOREIGN_KEY_CHECKS=0;
SET SQL_MODE="NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";


/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;

--
-- Database: `stackoverflow`
--

-- --------------------------------------------------------

--
-- Table structure for table `device`
--

CREATE TABLE IF NOT EXISTS `device` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=7 ;

--
-- Dumping data for table `device`
--

INSERT INTO `device` (`id`) VALUES
(1),
(2),
(3),
(4),
(5),
(6);

-- --------------------------------------------------------

--
-- Table structure for table `group`
--

CREATE TABLE IF NOT EXISTS `group` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=9 ;

--
-- Dumping data for table `group`
--

INSERT INTO `group` (`id`) VALUES
(1),
(2),
(3),
(4),
(5),
(6),
(7),
(8);

-- --------------------------------------------------------

--
-- Table structure for table `groups_have_devices`
--

CREATE TABLE IF NOT EXISTS `groups_have_devices` (
  `group_id` int(11) NOT NULL,
  `device_id` int(11) NOT NULL,
  PRIMARY KEY (`group_id`,`device_id`),
  KEY `device_id` (`device_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Dumping data for table `groups_have_devices`
--

INSERT INTO `groups_have_devices` (`group_id`, `device_id`) VALUES
(4, 6);

-- --------------------------------------------------------

--
-- Table structure for table `groups_have_people`
--

CREATE TABLE IF NOT EXISTS `groups_have_people` (
  `group_id` int(11) NOT NULL,
  `person_id` int(11) NOT NULL,
  PRIMARY KEY (`group_id`,`person_id`),
  KEY `person_id` (`person_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Dumping data for table `groups_have_people`
--

INSERT INTO `groups_have_people` (`group_id`, `person_id`) VALUES
(1, 2),
(5, 5);

-- --------------------------------------------------------

--
-- Table structure for table `groups_have_sites`
--

CREATE TABLE IF NOT EXISTS `groups_have_sites` (
  `group_id` int(11) NOT NULL,
  `site_id` int(11) NOT NULL,
  PRIMARY KEY (`group_id`,`site_id`),
  KEY `site_id` (`site_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Dumping data for table `groups_have_sites`
--

INSERT INTO `groups_have_sites` (`group_id`, `site_id`) VALUES
(2, 2),
(3, 4),
(6, 6),
(7, 8);

-- --------------------------------------------------------

--
-- Table structure for table `people_have_devices`
--

CREATE TABLE IF NOT EXISTS `people_have_devices` (
  `person_id` int(11) NOT NULL,
  `device_id` int(11) NOT NULL,
  PRIMARY KEY (`person_id`,`device_id`),
  KEY `device_id` (`device_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Dumping data for table `people_have_devices`
--

INSERT INTO `people_have_devices` (`person_id`, `device_id`) VALUES
(1, 1),
(2, 2),
(3, 3);

-- --------------------------------------------------------

--
-- Table structure for table `person`
--

CREATE TABLE IF NOT EXISTS `person` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=7 ;

--
-- Dumping data for table `person`
--

INSERT INTO `person` (`id`) VALUES
(1),
(2),
(3),
(4),
(5),
(6);

-- --------------------------------------------------------

--
-- Table structure for table `site`
--

CREATE TABLE IF NOT EXISTS `site` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=utf8 AUTO_INCREMENT=9 ;

--
-- Dumping data for table `site`
--

INSERT INTO `site` (`id`) VALUES
(1),
(2),
(3),
(4),
(5),
(6),
(7),
(8);

-- --------------------------------------------------------

--
-- Table structure for table `sites_have_devices`
--

CREATE TABLE IF NOT EXISTS `sites_have_devices` (
  `site_id` int(11) NOT NULL,
  `device_id` int(11) NOT NULL,
  PRIMARY KEY (`site_id`,`device_id`),
  KEY `device_id` (`device_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Dumping data for table `sites_have_devices`
--

INSERT INTO `sites_have_devices` (`site_id`, `device_id`) VALUES
(3, 4),
(4, 5);

-- --------------------------------------------------------

--
-- Table structure for table `sites_have_people`
--

CREATE TABLE IF NOT EXISTS `sites_have_people` (
  `site_id` int(11) NOT NULL,
  `person_id` int(11) NOT NULL,
  PRIMARY KEY (`site_id`,`person_id`),
  KEY `person_id` (`person_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8;

--
-- Dumping data for table `sites_have_people`
--

INSERT INTO `sites_have_people` (`site_id`, `person_id`) VALUES
(1, 1),
(2, 3),
(5, 4),
(6, 6);

--
-- Constraints for dumped tables
--

--
-- Constraints for table `groups_have_devices`
--
ALTER TABLE `groups_have_devices`
  ADD CONSTRAINT `groups_have_devices_ibfk_2` FOREIGN KEY (`device_id`) REFERENCES `device` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `groups_have_devices_ibfk_1` FOREIGN KEY (`group_id`) REFERENCES `group` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION;

--
-- Constraints for table `groups_have_people`
--
ALTER TABLE `groups_have_people`
  ADD CONSTRAINT `groups_have_people_ibfk_2` FOREIGN KEY (`person_id`) REFERENCES `person` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `groups_have_people_ibfk_1` FOREIGN KEY (`group_id`) REFERENCES `group` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION;

--
-- Constraints for table `groups_have_sites`
--
ALTER TABLE `groups_have_sites`
  ADD CONSTRAINT `groups_have_sites_ibfk_2` FOREIGN KEY (`site_id`) REFERENCES `site` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `groups_have_sites_ibfk_1` FOREIGN KEY (`group_id`) REFERENCES `group` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION;

--
-- Constraints for table `people_have_devices`
--
ALTER TABLE `people_have_devices`
  ADD CONSTRAINT `people_have_devices_ibfk_2` FOREIGN KEY (`device_id`) REFERENCES `device` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `people_have_devices_ibfk_1` FOREIGN KEY (`person_id`) REFERENCES `person` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION;

--
-- Constraints for table `sites_have_devices`
--
ALTER TABLE `sites_have_devices`
  ADD CONSTRAINT `sites_have_devices_ibfk_2` FOREIGN KEY (`device_id`) REFERENCES `device` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `sites_have_devices_ibfk_1` FOREIGN KEY (`site_id`) REFERENCES `site` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION;

--
-- Constraints for table `sites_have_people`
--
ALTER TABLE `sites_have_people`
  ADD CONSTRAINT `sites_have_people_ibfk_2` FOREIGN KEY (`person_id`) REFERENCES `person` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION,
  ADD CONSTRAINT `sites_have_people_ibfk_1` FOREIGN KEY (`site_id`) REFERENCES `site` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION;
SET FOREIGN_KEY_CHECKS=1;

/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;

这是查找每个组的所有子设备的查询。

SELECT
  `group`.`id` AS `group_id`,
  `device`.`id` AS `device_id`
FROM
  `group`
  INNER JOIN groups_have_devices
    ON (group.id=groups_have_devices.group_id)
  INNER JOIN device
    ON (groups_have_devices.device_id=device.id)

UNION ALL

SELECT
  `group`.`id` AS `group_id`,
  `device`.`id` AS `device_id`
FROM
  `group`
  INNER JOIN groups_have_people
    ON (group.id=groups_have_people.group_id)
  INNER JOIN person
    ON (groups_have_people.person_id=person.id)
  INNER JOIN people_have_devices
    ON (person.id=people_have_devices.person_id)
  INNER JOIN device
    ON (people_have_devices.device_id=device.id)

UNION ALL

SELECT
  `group`.`id` AS `group_id`,
  `device`.`id` AS `device_id`
FROM
  `group`
  INNER JOIN groups_have_sites
    ON (group.id=groups_have_sites.group_id)
  INNER JOIN site
    ON (groups_have_sites.site_id=site.id)
  INNER JOIN sites_have_devices
    ON (site.id=sites_have_devices.site_id)
  INNER JOIN device
    ON (sites_have_devices.device_id=device.id)

UNION ALL

SELECT
  `group`.`id` AS `group_id`,
  `device`.`id` AS `device_id`
FROM
  `group`
  INNER JOIN groups_have_sites
    ON (group.id=groups_have_sites.group_id)
  INNER JOIN site
    ON (groups_have_sites.site_id=site.id)
  INNER JOIN sites_have_people
    ON (site.id=sites_have_people.site_id)
  INNER JOIN person
    ON (sites_have_people.person_id=person.id)
  INNER JOIN people_have_devices
    ON (person.id=people_have_devices.person_id)
  INNER JOIN device
    ON (people_have_devices.device_id=device.id)
ORDER BY
  group_id

这是获取所有设备及其直接父级的查询。

SELECT
  device.id AS device_id,
  person.id AS person_id,
  NULL AS site_id,
  NULL AS group_id
FROM
  device
  INNER JOIN people_have_devices
    ON (device.id=people_have_devices.device_id)
  INNER JOIN person
    ON (people_have_devices.person_id=person.id)

UNION ALL

SELECT
  device.id AS device_id,
  NULL AS person_id,
  site.id AS site_id,
  NULL AS group_id
FROM
  device
  INNER JOIN sites_have_devices
    ON (device.id=sites_have_devices.device_id)
  INNER JOIN site
    ON (sites_have_devices.site_id=site.id)

UNION ALL

SELECT
  device.id AS device_id,
  NULL AS person_id,
  NULL AS site_id,
  group.id AS group_id
FROM
  device
  INNER JOIN groups_have_devices
    ON (device.id=groups_have_devices.device_id)
  INNER JOIN `group`
    ON (groups_have_devices.group_id=group.id)

您可以像这样进一步获取特定个人、组或网站的直接子设备

SELECT
  device_id
FROM (
  SELECT
    device.id AS device_id,
    NULL AS person_id,
    site.id AS site_id,
    NULL AS group_id
  FROM
    device
    INNER JOIN sites_have_devices
      ON (device.id=sites_have_devices.device_id)
    INNER JOIN site
      ON (sites_have_devices.site_id=site.id)
) sub_query
WHERE
  sub_query.site_id='3'
于 2013-06-07T18:30:42.177 回答
0

解决此问题的另一种方法是将一些表拆分为多个表，然后将它们全部重新组合在一起。

这稍微复杂一些，但可以提供更大的正确性保证。

（我已经一周不接受@amaster507 的回答，希望能得到一些关于这个解决方案的意见。）

要求：

group
-----
id

site
----
id
group_id (optional)

person
------
id
group_id (one of these two must exist 
site_id   and the other must be null)

device
------
id 
group_id  (one of these three must exist 
site_id    and the others must be null)
person_id

提议的架构：

group
-----
id

site
----
id
group_id (optional)

person_in_group
---------------
id
group_id  

person_at_site
--------------
id
site_id   

device_in_group
---------------
id 
group_id   

device_at_site
--------------
id 
site_id   

device_with_person
------------------
id 
person_id

现在需要对UNION ALLperson_in_group 和 person_at_site 表中的一个进行本应在 person 表上进行的查询。

同样，现在需要针对UNION ALLdevice_in_group、device_at_site 和 device_with_person 表中的一个对设备表进行查询。

于 2013-10-03T07:36:29.193 回答