问题描述
我想知道一个关系模式是否在BCNF中使用单一属性键，它会自动在4NF吗？
I would like to know if a relational schema is in BCNF with a single-attribute key, will it automatically be in 4NF?
我试图使用表格，但是如果答案是肯定的，我怎么才能正式证明它没有绘制表格。
I tried to derive it using table but how can I formally prove it without drawing table if the answer is yes.
推荐答案
书籍证明：
- BCNF和所有键简单⟹5NF
- BCNF和任何键简单⟹4NF
难度将找到合适的书。
[... time passeth ...书架的模糊部分正在搜索...]
我第一次遇到这本书的书是：
The book where I first came across it is:
- 。定理在第29章保证关系数据库中更高正常形式的简单条件。
- Relational Database: Writings 1989-1991. The theorems are in chapter 29, "Simple conditions for guaranteeing higher normal forms in relational databases".
它也由ACM发布：
（您可能需要获得该网页的权限。）
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我的记忆轻微不准确;正确的定理是：
My memory was mildly inaccurate; the correct theorems are:
- 3NF和所有键简单⟹5NF
- BCNF和任何键简单⟹4NF
第一个结果比我最初声明的稍微强一些，因为BCNF中的所有关系都在3NF中，不在BCNF。第二个是正确的。
The first result is slightly stronger than I originally stated because all relations in BCNF are also in 3NF but some relations in 3NF are not in BCNF. The second was correctly stated.
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