谁能用一个正确的例子向我解释1NF，2NF，3NF，BCNF规则？ [英] Can anyone explain me 1NF, 2NF, 3NF, BCNF rules with a proper example?

问题描述

这是一个常见的面试问题。我面对一次面试，面试官给了我一张桌子，问我告诉他桌子的正常形式是什么？如果它在## NF中，则将其归一化到下一个NF？

This is a common interview question. I faced one interview where the interviewer gave me one table and asked me tell him which normal form the table is in? If it's in ##NF, then normalize it to the next NF?

我总是对这些正常数据库形式感到困惑。
谁能向我解释这些正常形式，并举例说明如何将每个NF建模到表格中，以便对我的下一次面试有所帮助？

I'm always get confused between these normal forms of database. Can anyone explain to me these normal forms with a proper example of how each NF is modeled into table so it will help in my next interview?

推荐答案

Boyce Codd范式实际上是最重要的，也是最容易解释的：每个不重要的行列式都是一个超键（只要记住超键中的箭头）。较小的范式仅值得一提，因为在某些情况下BCNF不能保持依赖关系。

Boyce Codd Normal Form is really the most important and also the easiest to explain: Every non-trivial determinant is a superkey (just remember "arrows out of superkeys"). The lesser normal forms are only worth mentioning because BCNF is not dependency-preserving in a few cases.

休·达文（Hugh Darwen）的BCNF和5NF示例：

Examples of BCNF and 5NF by Hugh Darwen:

• 数据库设计问题：第一部分


• 数据库设计问题：第二部分

• Database Design Issues: Part I
• Database Design Issues: Part II

更多数学定义（Abiteboul等人）：

For more mathematical definitions (Abiteboul et al):

• 数据库基础：逻辑级别

• Foundations of Databases: The Logical Level

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