需要归一化理论解释 [英] Normalization Theory Explanation needed

问题描述

我正在查看带有复合主键的关系的特定示例。基于其功能依赖性，我知道它在1NF中。在将其标准化为3NF时，我遇到了一种尚未遇到的情况。我遵循了所有部分依赖项和传递性依赖项的步骤，但是规范化为3NF的最后一步要求您创建一个包含主键和所有依赖于此的非主键属性的关系。

I'm looking at a specific example of a relation with a composite primary key. Based on its functional dependencies, I know it is in 1NF. While normalizing it to 3NF I came across a situation I have not yet encountered. I followed the steps for all partial dependencies and transitive dependencies, but the last step of normalizing to 3NF requires you to create a relation that contains the primary key and all non-prime attributes dependent on it.

在我的特定情况下，我具有主键，但是没有主功能键。我是否要制作仅包含复合主键的表？还是我根本不做一个？

In my specific case, I have the primary key, but no full functional dependencies on it. Do I make a table containing only my composite primary key? Or do I not make one at all?

我对复合键和主键没有困惑。请参阅下面的评论，以了解为什么我认为我的问题与那个问题不同

I have no confusion of composite and primary keys. See my comment below to see why I believe my question is different from that one

推荐答案

由一个组合键组成，没有其他属性。它不仅在理论上有效，而且还发生在现实世界中。

It is perfectly legitimate to have a relation that consists of a composite key and no other attributes. It's not only theoretically valid, but also it happens in the real world.

在这种情况下，这种关系仅是断言存在由复合密钥标识的事物。数据的用户将使用它来测试是否存在，而不是像通常使用具有非关键属性的关系那样来进行查找。

In such situation, that relation is merely asserting the existence of something identified by the composite key. And it would be used by the user of the data to test for existence and not for the same kind of lookups that a relation with non key attributes is typically used for.

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