《数据库系统概论》| 第六章关系数据理论知识梳理

柔情只为你懂 2023-10-06 11:43 27阅读 0赞

> ## 关系数据理论 ##

**目录**

关系数据理论

6.1 问题的提出

1、一个关系模式可能存在的问题有哪些？

6.2 规范化

6.2.1 函数依赖

2、函数依赖：能区分不同的函数依赖

1.函数依赖

2.平凡函数依赖与非平凡函数依赖

3.完全函数依赖与部分函数依赖

4.传递函数依赖

6.2.2 码 (了解）

6.2.3 范式

6.2.4 2NF

6.2.5 3NF

6.2.6 BCNF

6.2.7 多值依赖

6.2.8 4NF

6.2.9 规范化小结

6.3 数据依赖的公理系统

\*6.4 模式的分解

6.5 小结

--------------------

1、一个关系模式可能存在的问题有哪些？

2、函数依赖：能区分不同的函数依赖

**包括：函数依赖、平凡函数依赖与非平凡函数依赖、完全函数依赖、部分函数依赖、传递函数依赖的定义理解和应用（即能区分不同的函数依赖）**

3、在函数依赖范畴，范式：

![20190113155449560.png][]

5、1NF、2NF、3NF、BCNF的定义和判别；p182

6、关系模式候选码的求解(看课件)；

8、根据文字描述，判断关系的函数依赖，由函数依赖再来判断是否存在部分，传递依赖，会分析判断不好的依赖带来的操作麻烦和异常。

### 6.1 问题的提出 ###

![20190113155803956.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70][]![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 1][]

#### 1、一个关系模式可能存在的问题有哪些？ ####

（1）数据冗余 （浪费大量的存储空间）

（2）更新异常（Update Anomalies） （数据冗余 ，更新数据时，维护数据完整性代价大。）

（3）插入异常（Insertion Anomalies）

（4）删除异常（Deletion Anomalies）

### 6.2 规范化 ###

#### 6.2.1 函数依赖 ####

#### 2、函数依赖：能区分不同的函数依赖 ####

**（包括：函数依赖、平凡函数依赖与非平凡函数依赖、完全函数依赖、部分函数依赖、传递函数依赖的定义理解和应用）**

*  #### **1.函数依赖**  ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 2][]

**X对Y有明确的对应关系**

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 3][]

![20190113161610314.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 4][]

*  #### **2.平凡函数依赖与非平凡函数依赖**  ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 5][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 6][]

*  #### **3.完全函数依赖与部分函数依赖**  ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 7][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 8][]

*  #### **4.传递函数依赖** ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 9][]

#### 6.2.2 码 (了解） ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 10][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 11][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 12][]

![20190113163245775.png][]

#### 6.2.3 范式 ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 13][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 14][]

#### 6.2.4 2NF ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 15][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 16][]![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 17][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 18][]![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 19][]

#### 6.2.5 3NF ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 20][]

#### 6.2.6 BCNF ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 21][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 22][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 23][]

#### 6.2.7 多值依赖 ####

#### 6.2.8 4NF ####

#### 6.2.9 规范化小结 ####

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 24][]

![2019011318181289.png][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzQxNTIzMDk2_size_16_color_FFFFFF_t_70 25][]

### 6.3 数据依赖的公理系统 ###

函数依赖闭包

### \*6.4 模式的分解 ###

### 6.5 小结 ###

[20190113155449560.png]: https://img-blog.csdnimg.cn/20190113155449560.png
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