introduction

course goals

the basics of how to use and manage data how to design and create such database; use them (via sql query language) implement

definitions

• dbms=data base management system; a piece of software designed to store and manage database; ep. mysql,oracle

• database system: dbms+data+application programs

使用它的原因

如果使用文件系统，在源代码中描述数据的类型（元数据metadata）使得想使用数据的人必须访问源代码； 为防止并发操作出现问题 处理文件封锁和解锁的源代码会相当复杂

它是咋工作的

metadata=catalog=data dictionary

sql:ddl dml

• sql 支持任何复杂查珣和更新操作
• 数据操作语言的特点：声明式
• 模式与数据的关系：schema-types;instances-variable

数据项存储 数据模型

数据库中的数据是按照一定的逻辑结构存放的，这种结构用数据模型来表示

分类

• relational
• key/value
• graph
• document/xml/object

• wide-column/column-family

• array/matrix/vectors(machine learning)

(obsolete/legacy/rare) * hierarchical * network * multi-value

关系模型的术语

• tables--relations
• columns--attributes
• rows--tuples
• schema(e.g.:acc_schema=(bname,acct_no,balance))

foundamental concepts

data independence

• concepts:applications do not need to worry about how the data is structured and stored

• logical data independence逻辑独立性

• protection from changes in the logical structure of the data;
• can add(drop) column/table;
• physical data independence物理独立性
• protection from physical layout changes
• can add index;change record order

## dbms users

• implementer(build system)
• designer(establishes schema)
• application developer(progams that operate on databasae)
• adminster(dba):loads data,keeps running smoothly top

## overall system architecture

• file&system structure
  • records in blocks,dictionary,buffer management
• indexing & hashing
  • b-trees,hashing
• query processing
  • query costs,join strategies
• crash recovery
  • failures,stable storage
• concurrency control
  • correctness,locks
• transaction processing
  • logs,deadlocks

## 构建一个db应用的步骤

0.选择应用领域 1.conceptual design * an er diagram of the app.domain 2.选择一个dbms类型 3.