关系数据库规范化问题

Question

我的网站是求职网站。有三种类型的用户：User，Employee或Admin。

• User可以搜索和申请工作，
• Employee可以发布职位信息，浏览器恢复，
• Admin是管理网站。

这里是我定义的所有表格。

-- Users table, users = jobseekers, containing jobseekers info 
DROP TABLE IF EXISTS users; 
CREATE TABLE users (
    user_id INT UNSIGNED NOT NULL AUTO_INCREMENT, 
    first_name VARCHAR(20) NOT NULL, 
    last_name VARCHAR(40) NOT NULL, 
    email VARCHAR(80) NOT NULL, 
    pass CHAR(60) NOT NULL, 
    user_phone VARCHAR(11) NOT NULL, 
    user_address VARCHAR(250) NOT NULL, 
    active CHAR(32) NULL, 
    last_login_time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP 
            ON UPDATE CURRENT_TIMESTAMP, 
    last_login_ip VARCHAR(15) NOT NULL, 
    registration_time DATETIME NOT NULL, 
    registration_ip VARCHAR(15) NOT NULL, 
    PRIMARY KEY (user_id), 
    UNIQUE KEY (email), 
    INDEX login (email, pass) 
) ENGINE = INNODB; 


-- Employers table, containing employers info 
DROP TABLE IF EXISTS employers; 
CREATE TABLE employers (
    employer_id INT UNSIGNED NOT NULL AUTO_INCREMENT, 
    first_name VARCHAR(20) NOT NULL, 
    last_name VARCHAR(40) NOT NULL, 
    company_name VARCHAR(80) NOT NULL, 
    email VARCHAR(80) NOT NULL, 
    pass CHAR(40) NOT NULL, 
    employer_phone VARCHAR(11) NOT NULL, 
    employer_mobile VARCHAR(11), 
    employer_address VARCHAR(250) NOT NULL, 
    active CHAR(32) NULL, 
    last_login_time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP 
            ON UPDATE CURRENT_TIMESTAMP, 
    last_login_ip VARCHAR(15) NOT NULL, 
    registration_time DATETIME NOT NULL, 
    registration_ip VARCHAR(15) NOT NULL, 
    PRIMARY KEY (employer_id), 
    UNIQUE KEY (email), 
    INDEX login (email, pass) 
) ENGINE = INNODB; 


-- Administrators table, containing site administrators info 
-- Note: move created_time after last_login_time, otherwise SQL error #1293 
DROP TABLE IF EXISTS administrators; 
CREATE TABLE administrators (
    admin_id INT UNSIGNED NOT NULL AUTO_INCREMENT, 
    first_name VARCHAR(20) NOT NULL, 
    last_name VARCHAR(40) NOT NULL, 
    email VARCHAR(80) NOT NULL, 
    pass CHAR(40) NOT NULL, 
    last_login_time TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP 
            ON UPDATE CURRENT_TIMESTAMP, 
    last_login_ip VARCHAR(15) NOT NULL, 
    created_time DATETIME NOT NULL, 
    PRIMARY KEY (admin_id) 
) ENGINE = INNODB; 


-- CVs table, containing CV info 
DROP TABLE IF EXISTS cvs; 
CREATE TABLE cvs (
    cv_id INT(10) UNSIGNED NOT NULL auto_increment, 
    cv_name VARCHAR(60) NOT NULL, 
    user_id INT UNSIGNED NOT NULL, 
    description VARCHAR(80), 
    PRIMARY KEY (cv_id) 
) ENGINE = INNODB; 


-- Jobs table, containing job information 
-- Note: must use MYISAM to support Fulltext search 
DROP TABLE IF EXISTS jobs; 
CREATE TABLE jobs (
    job_id INT(10) UNSIGNED NOT NULL auto_increment, 
    job_title VARCHAR(30) NOT NULL, 
    employer_id INT UNSIGNED NOT NULL, 
    company_name VARCHAR(80) NOT NULL, 
    description TEXT NOT NULL, 
    town VARCHAR(30) NOT NULL, 
    county VARCHAR(30) NOT NULL, 
    contact_name VARCHAR(40) NOT NULL, 
    contact_phone VARCHAR(11) NOT NULL, 
    contact_email VARCHAR(80) NOT NULL, 
    salary SMALLINT(5) UNSIGNED NOT NULL, 
    confirm TINYINT(1) UNSIGNED NOT NULL default 0, 
    posted_time TIMESTAMP NOT NULL, 
    deadline INT(10) UNSIGNED NOT NULL, 
    job_status SET('open', 'closed') NOT NULL, 
    employer_paid SET('yes', 'no') NOT NULL, 
    PRIMARY KEY (job_id), 
    FULLTEXT (job_title, description) 
) ENGINE = MYISAM; 


-- Jobs users applied 
DROP TABLE IF EXISTS jobs_applied; 
CREATE TABLE jobs_applied (
    jobs_applied_id INT(10) UNSIGNED NOT NULL auto_increment, 
    user_id INT UNSIGNED NOT NULL, 
    cv_id INT(10) UNSIGNED NOT NULL, 
    cv_name VARCHAR(60) NOT NULL, 
    job_id INT(10) unsigned NOT NULL, 
    job_title VARCHAR(30) NOT NULL, 
    company_id INT(10) unsigned NOT NULL, 
    company_name VARCHAR(80) NOT NULL, 
    applied_time TIMESTAMP NOT NULL, 
    PRIMARY KEY (jobs_applied_id) 
) ENGINE = INNODB; 


-- Reports table, containing info to produce site reports 
DROP TABLE IF EXISTS reports; 
CREATE TABLE reports (
    report_id INT(10) UNSIGNED NOT NULL auto_increment, 
    user_id INT UNSIGNED NOT NULL, 
    employer_id INT UNSIGNED NOT NULL, 
    job_id INT(10) unsigned NOT NULL, 
    job_title VARCHAR(30) NOT NULL, 
    job_posttime TIMESTAMP NOT NULL, 
    content VARCHAR(250) NOT NULL, 
    report_time INT(10) UNSIGNED NOT NULL, 
    PRIMARY KEY (report_id) 
) ENGINE = INNODB; 

有人说我设计的表格正是我在关系数据库中不能做的，因为它们充满了重复。我不明白。任何人都请看看我的设计，并指出设计错误？

Answer 1

您需要规范化数据库架构/设计以避免存储重复数据。

请参阅这篇文章标准化与实例：Description of the database normalization basics

你的具体情况，你应该分离出Company，Contact，JobLocation，JobType，JobIndustry等转化为自己的表，并利用关系将它们连接。

Answer 2

最大跳出我的问题（尽管有一些）是雇主和管理员字段的一半实际上只是用户/授权管理的一部分。保持'搜索者'和'雇主'和'管理员'的概念是分开的（单独的表格很好，并且实际上会帮助FK关系），但是应该有一个统一的“用户/账户”关系。

例如，想象三个“角色区分”表。用户可以通过DRI与零或全部三个关联（SQL本身并不支持分布式FK），因此应该制定业务规则以确保正确的关联 - 但为什么雇主也不能成为搜索者？

这些表格可以包含额外的信息，如涉及具体的角色（Seeker，Employer，Admin）。保留单独的表格（而不仅仅是一个歧视角色栏）的好处是：

1. 可以根据需要将附加列添加到精制类型;
2. FK可以沿着role_id建立，而不需要两部分（user_id，角色）。

Seekers (people looking for jobs) 
--- 
seeker_id (PK) 
user_id (FK Users, not null) 

Employers 
--- 
employer_id (PK) 
user_id (FK Users, not null) 

Administrators 
--- 
admin_id (PK) 
user_id (FK Users, not null) 

Users/Accounts 
--- 
- All the data that relates to login/authorization information such as username 
- and password salt/hash, account contact e-mail, etc. 
- You probably want to separate the authentication such as login/auth information 
- and additional details, such as "last login from" or "registered from", etc. 

最“CMS”系统已经具有认证和授权方案的地方。

---

应该归（但打我远远低于上面讨论的重复的）其他的事情都是“联系信息”和“公司/位置”。将“Job”与“JobListing”分开也许是值得的。此外，还有似乎是某些字段只是没有理由重复：

company_id INT(10) unsigned NOT NULL, 
company_name VARCHAR(80) NOT NULL, 

由于关系已经有COMPANY_ID的FK /加入，company_name列，被简单地复制数据，应予删除。