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| ```mermaid | ||
| flowchart LR | ||
| 0{概述} | ||
| 0-->1 | ||
| 1[View Of Data]-->2[Data Abstraction] | ||
| 1-->b[Data Models] | ||
| 0-->0.1[Schema and instances 模式与实例] | ||
| 0.1-->区分 | ||
| 0.1-->0.1.1[Physical Data Independence] | ||
| 0-->1.2[Language] | ||
| 1.2-->1.2.1[DDL:Data Difinition Language] | ||
| 1.2-->1.2.2[DML:Data Manipulation Language] | ||
| 1.2.2-->声明式:SQL | ||
| 1.2.2-->过程式 | ||
| 0-->4[Database Design] | ||
| 4-->4.1[E-R模型 实体-联系模型] | ||
| 4-->4.2[规范化] | ||
| 0-->3[Database Engine] | ||
| 3-->1.8 | ||
| 3-->3.2[Storage Manager] | ||
| 3-->3.3[The Query Processor] | ||
| 3.3-->3.3.1[DDL interpreter] | ||
| 3.3-->3.3.2[DML compiler] | ||
| 3.3-->3.3.3[Query evaluation engine] | ||
| 1.8[事务管理器]-->1.8.1[并发控制管理器] | ||
| 1.8-->1.8.2[恢复管理器] | ||
| ``` | ||
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| - **Database Management System (DBMS)** | ||
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| > A **database** system is a collection of interrelated **data** and a set of **programs** that allow users to access and modify these data. | ||
| **Characteristics of Databases** | ||
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| data persistence (数据持久性) | ||
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| convenience in accessing data (数据访问便利性) | ||
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| data integrity (数据完整性) | ||
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| concurrency control for multiple user (多用户并发控制) | ||
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| failure recovery (故障恢复) | ||
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| security control (安全控制) | ||
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| ## View Of data | ||
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| ## Language | ||
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| ### DDL | ||
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| **Data dictionary** contains metadata | ||
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| - 数据模式 | ||
| - 完整性约束 | ||
| - 授权 | ||
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| ### DML | ||
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| **SQL** | ||
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| - A query takes as **input several** **tables** (possibly only one) and always returns **a single table**. | ||
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| - **SQL does not support** actions such as input from users, output to | ||
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| displays, or communication over the network. | ||
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| # Physical Storage | ||
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| ## Overview | ||
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| ## Flash Memory | 闪存 | ||
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| ## Magnetic Disk | ||
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| <img src="https://zzh-pic-for-self.oss-cn-hangzhou.aliyuncs.com/img/202405062255334.png" alt="image-20240506225525215" style="zoom:50%;" /> | ||
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| - 通过机械运动，比较慢 | ||
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| ### Performance | ||
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| - 上面的IOPS支持的操作是Random的R/W | ||
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| ### Optimization | ||
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| # Data Storage Structures | ||
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| ## |
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| # Relation | ||
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| > § Structure of Relational Databases | ||
| > | ||
| > § Database Schema 数据库模式 | ||
| > | ||
| > - A relation instance *r* defined over schema *R* is denoted by *r* (*R*) | ||
| > | ||
| > § Keys | ||
| > | ||
| > § Schema Diagrams | ||
| > | ||
| > § Relational Query Languages | ||
| > | ||
| > § The Relational Algebra | ||
| ## Structure of Relational Databases | ||
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| ### Attributes | ||
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| - 原子性 --> 不可拆分（数组、结构体之类不可） | ||
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| - The set of allowed values for each **attribute** is called the **domain** **（域）** of the attribute | ||
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| - The special value **null** **（空值）** is a member of every domain. Indicated that the value is “unknown” | ||
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| - 无序性，顺序没有影响 | ||
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| ## Database Schema 数据库模式 | ||
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| ## Keys | ||
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| - primary key 的约束条件 | ||
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| - Foreign | ||
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| - $R_1$中的一个属性，是另外一个参照$R_2$的 primary key | ||
| - 约束条件比较强，必须是 A的属性 B的`primary key` | ||
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| - referential integrity constraint 参照完整性约束 | ||
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| - 约束条件较弱， | ||
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| ## Database | ||
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| ## Relation Algebra | ||
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| - project 竖向选择 |
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