函数依赖，闭包，覆盖，最小化基本集，部分函数依赖与完全函数依赖，传递函数依赖，候选键，外来建，逻辑蕴含

﹏ヽ暗。殇╰゛Y 2024-03-31 08:51 158阅读 0赞

**简介**：本文讲解函数依赖，闭包，覆盖，最小化基本集，部分函数依赖与完全函数依赖，传递函数依赖，候选键，外来建，逻辑蕴含。

## 函数依赖 ##

### 定义 ###

![在这里插入图片描述][3aee3053f5a6404fa19d453064e0f575.png]

### 示例 ###

![在这里插入图片描述][5ef200904308496faa3b0f8c0f351d65.png]

### 特性 ###

![在这里插入图片描述][9fae444de0c54d7abfd0a0605bb83126.png]

### 练习 ###

![在这里插入图片描述][62ef2e2d9a4d4995b1fe73bf3f67c1e9.png]  
![在这里插入图片描述][51e696a89c6b4fd792bf6d2325ea106d.png]

## 部分函数依赖与完全函数依赖 ##

### 定义 ###

![在这里插入图片描述][f16e061a172343929faeaf9a24e1a97e.png]

### 练习 ###

![在这里插入图片描述][f9818dc2cc764fb98ae054cb3c3caaed.png]

## 传递函数依赖 ##

### 定义 ###

![在这里插入图片描述][0e0b04f5b2534b9ca9c0a61859624f74.png]

### 练习 ###

![在这里插入图片描述][4a4aebf4ac6144f68691648076c1d0de.png]  
![在这里插入图片描述][d64a5711f9ea437b9cac5ff82161554c.png]

## 候选键 ##

### 定义 ###

![在这里插入图片描述][565e6c9caf29462c86550e748adff10e.png]

### 练习 ###

![在这里插入图片描述][1648450e187c408a9c8d49f6c18f505c.png]  
![在这里插入图片描述][219a165aceb645b487a1041931d2e015.png]  
![在这里插入图片描述][9aa9e2bb041e4da9bcb117839ca03d50.png]

## 外来键 ##

### 定义 ###

![在这里插入图片描述][15ae0f02ffbc456a903ff1adf2b74ae4.png]

## 逻辑蕴涵 ##

### 定义 ###

![在这里插入图片描述][68e3a4c9a13e469689962e61c607674f.png]

## 闭包 ##

### 定义 ###

![在这里插入图片描述][766a7a887c624d1f9fb0a48cc2601f08.png]

### 属性闭包计算方法 ###

![在这里插入图片描述][1034cda3d2be48aab3b8a6d6ad2855d0.png]

### 例题 ###

![在这里插入图片描述][ce4885db79af43228fa2022f06bbbe11.png]  
![在这里插入图片描述][a12d6a8a765a450b834ff3a32adc1ce5.png]

## 覆盖 ##

### 定义 ###

![在这里插入图片描述][3ea298626a1c4dc1bbe520e7735878db.png]

## 最小化基本集 ##

![在这里插入图片描述][4c230e736d644d689b9a23cc6caab825.png]  
![在这里插入图片描述][e070ed70b34448a1b64694ceed26f03f.png]

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