如何在数据库中建模这个类? [英] How can I model this class in a database?
问题描述
我需要一点帮助。这是我的设计,以组织几个类别。
类别1
子类别1.1
子类别1.1。 1
子类别1.2
子类别1.3
这将是一个集合。我想把它存储在一个数据库,但我不知道如何在数据库表中建模。我使用的是SQL Server CE。
UPDATE :
我忘记将目标号码类(1.1,1.1.1)。
$ b
- 类别
- id(主键,非空)
/ ul>
然后,如果类别有父级,则引用该另一行的 id
。所以表是自引用的。顶级类别有一个null parent_category_id
。
建立这样的表格时, t创建循环引用。
I need a little of help. This is my design to organize several categories.
Category 1
Sub Category 1.1
Sub Category 1.1.1
Sub Category 1.2
Sub Category 1.3
It would be a collection. I want to store it in a database, but I don't know how can I model it in a database table. I'm using SQL Server CE.
UPDATE:
I forgot put the objective number in the class (1.1, 1.1.1).
You'd have a table something like this:
- category
- id (primary key, not null)
- name (text, not null)
- parent_category_id (foreign key to category.id, nullable)
Then, if a category has a parent, you reference the id
of that other row. So the table is self-referential. Toplevel categories have a null parent_category_id
.
When building tables like this you do need to be careful that you don't create a circular reference.
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