为什么我的 SQL 表不是 3 范式

Question

我已经制作了这个数据库。看起来它工作正常，除了我被告知我的表“事件”不是第三范式。我不明白为什么它不是第三范式。我认为这可能是因为城市和邮政编码应该总是相同的，但是大城市可以有多个邮政编码，我没有看到为城市及其邮政编码创建另一个表的意义，相关到事件表。

如果使用系统保留的某些名称错误地命名了某些名称或属性，也很抱歉。我不得不把代码翻译成英文，因为我是用我的母语写的:)。感谢您的帮助。

Create table [article]
(
    [id_article] Integer Identity(1,1) NOT NULL,
    [id_author] Integer NOT NULL,
    [id_category] Integer NOT NULL,
    [title] Nvarchar(50) NOT NULL,
    [content] Text NOT NULL,
    [date] Datetime NOT NULL,
Primary Key ([id_article])
) 
go

Create table [author]
(
    [id_author] Integer Identity(1,1) NOT NULL,
    [name] Nvarchar(25) NOT NULL,
    [lastname] Nvarchar(25) NOT NULL,
    [email] Nvarchar(50) NOT NULL, UNIQUE ([email]),
    [phone] Integer NOT NULL, UNIQUE ([phone]),
    [nick] Nvarchar(20) NOT NULL, UNIQUE ([nick]),
    [passwd] Nvarchar(50) NOT NULL,
    [acc_number] Integer NOT NULL, UNIQUE ([acc_number]),
Primary Key ([id_author])
) 
go

Create table [event]
(
    [id_event] Integer Identity(1,1) NOT NULL,
    [id_author] Integer NOT NULL,
    [name] Nvarchar(50) NOT NULL,
    [date] Datetime NOT NULL, UNIQUE ([date]),
    [city] Nvarchar(50) NOT NULL,
    [street] Nvarchar(50) NOT NULL,
    [zip] Integer NOT NULL,
    [house_number] Integer NOT NULL,
    [number_registered] Integer Default 0 NOT NULL Constraint [number_registered] Check (number_registered <= 20),
Primary Key ([id_event])
) 
go

Create table [user]
(
    [id_user] Integer Identity(1,1) NOT NULL,
    [name] Nvarchar(15) NOT NULL,
    [lastname] Nvarchar(25) NOT NULL,
    [email] Nvarchar(50) NOT NULL, UNIQUE ([email]),
    [phone] Integer NOT NULL, UNIQUE ([phone]),
    [passwd] Nvarchar(50) NOT NULL,
    [nick] Nvarchar(20) NOT NULL, UNIQUE ([nick]),
Primary Key ([id_user])
) 
go

Create table [commentary]
(
    [id_commentary] Integer Identity(1,1) NOT NULL,
    [content] Text NOT NULL,
    [id_article] Integer NOT NULL,
    [id_author] Integer NULL,
    [id_user] Integer NULL,
Primary Key ([id_commentary])
) 
go

Create table [category]
(
    [id_category] Integer Identity(1,1) NOT NULL,
    [name] Nvarchar(30) NOT NULL,
Primary Key ([id_category])
) 
go

Create table [registration]
(
    [id_user] Integer NOT NULL,
    [id_event] Integer NOT NULL,
Primary Key ([id_user],[id_event])
) 
go


Alter table [commentary] add  foreign key([id_article]) references [article] ([id_article])  on update no action on delete no action 
go
Alter table [article] add  foreign key([id_author]) references [author] ([id_author])  on update no action on delete no action 
go
Alter table [event] add  foreign key([id_author]) references [author] ([id_author])  on update no action on delete no action 
go
Alter table [commentary] add  foreign key([id_author]) references [author] ([id_author])  on update no action on delete no action 
go
Alter table [registration] add  foreign key([id_event]) references [event] ([id_event])  on update no action on delete no action 
go
Alter table [commentary] add  foreign key([id_user]) references [user] ([id_user])  on update no action on delete no action 
go
Alter table [registration] add  foreign key([id_user]) references [user] ([id_user])  on update no action on delete no action 
go
Alter table [article] add  foreign key([id_category]) references [category] ([id_category])  on update no action on delete no action 
go

编辑： 你认为它可以这样工作吗？我创建了另一个名为 location 的表，其中包含以前在事件表中的所有地址信息，并创建了 id_event PFK。

Create table [event]
(
    [id_event] Integer Identity(1,1) NOT NULL,
    [id_author] Integer NOT NULL,
    [name] Nvarchar(50) NOT NULL,
    [datr] Datetime NOT NULL,
    [number_registered] Integer Default 0 NOT NULL Constraint [number_registered] Check (number_registered <= 20),
Primary Key ([id_event])
) 
go


Create table [location]
(
    [city] Char(1) NOT NULL,
    [id_event] Integer NOT NULL,
    [street] Char(1) NOT NULL,
    [house_number] Char(1) NOT NULL,
    [zip] Char(1) NOT NULL,
Primary Key ([id_event])
) 
go


Alter table [event] add  foreign key([id_auhtor]) references [author] ([id_author])  on update no action on delete no action 
go

Alter table [location] add  foreign key([id_event]) references [event] ([id_event])  on update no action on delete no action 
go

Answer 1

回答问题。

你是对的，数据库不是第三范式。如您所见，有机会规范化各种邮政编码、城市和街道。这将导致每个邮政编码（等）都有一行，并且每个邮政编码都有 FK。

就我个人而言，我不这样做。这显然取决于应用程序，但在我的系统中，我更感兴趣的是获取用户的地址，而不是所有具有特定邮政编码的用户。

根据您打算如何使用数据，第三法线可能不是存储数据的最有效方式。

Answer 2

根据您的编辑 - 关闭，但我会扭转它。我会给location 一个location_id 列（PK），删除它的event_id 列，然后使event 成为：

Create table [event]
(
    [id_event] Integer Identity(1,1) NOT NULL,
    [id_author] Integer NOT NULL,
    id_location Integer NOT NULL, /* Or null? does every event have to have a location */
    [name] Nvarchar(50) NOT NULL,
    [datr] Datetime NOT NULL,
    [number_registered] Integer Default 0 NOT NULL Constraint [number_registered] Check (number_registered <= 20),
Primary Key ([id_event])
) 

然后也反转外键。

这样，如果一个地址需要更正，它只需要在一行中进行更正 - 毕竟这是标准化的一点 - 只需应用一次更正。