1.데이터베이스(DataBase)란

1.1 DataBase Management System(DBMS)

DBMS contains information about a particular enterprise

ex)  Banking : transactions

     Airlines : reservations, schedules

     Universities : registration, grades

Manufacturing : production, inventory, orders, supply chain etc..

1.2 Purpose of Database Systems

데이터 베이스를 사용하는 이유는 대부분 정보를 저장하기 위해서이다.

1. Data redundancy and inconsistency
2. Difficulty in accessing data
3. Data isolation - multiple files and formats
4. integrity problems
5. Atomicity of updates
6. Concurrent access by multiple users
7. Security problems

1.3 View of Data

• Physical level : describes how a record is stored.
• Logical level : describes data stored in database and the relationships among the data
• View level : application programs hide details of data types. can also hide information for security

 - Architecture for a databse system

• Schema : the logical structure of the database

  Analogous to type information of a variable in a program

-Physical Schema : database desigan at the physical level

-Logical Schema : database design at the logical level

• Instance : the actual content of the database at a particular point in time 

  Analogous to the value of a variable

• Physical Data Independence : Ability to modify the physical shema without changing the logical schema

- 하지만 대부분 심각하게 영향을 주지는 않는다.

• Data Models  

1. Relation model
2. Entity-relationship data model
3. Object-based data models
4. Semistructured data model (XML) ETC..

1.4 Database Language

• Data Definition Language(DDL) : Specify the database schema

• Data Mnipulation Language(DML) : Express database queries and updates

보통 두개로 나누어진다. 하지만 두개가 완전히 분리되있는 것은 아니고 SQL 언어의 한 부분이다.

DDL

-Specification notation for defining the database schema

-DDL compiler generates a set of table templates stored in a data dictionary

-Data Dictionary contains metadata

Database schema

Integrity constraints

§Primary key (ID uniquely identifies instructors)

§Referential integrity(references constrint in SQL )

DML

-Accessing and manipulating the data organized by the appropriate data model

-DML은 Query Language이다

-Two classes of languages

§Procedural - user specifies what data is reuired and how to get those data

§Declarative(nonprocedural) - user specifies what data is required without specifying how to get those                               data

1.5 Relation Model

2장에서 다시 언급하겠다

*SQL : widely used non-procedural language

보통 프로그램은 데이터베이스에 접근하기 위해 다음 것들 중하나를 이용한다

-Language extensions to allow embedded SQL

-Application program interface which allow SQL queries to be sent to a database

1.6 Database Design

Logical Design : Deciding on the database schema. Database design requires that we find a "good" collection                 of relation schemas

Physical Design : Deciding on the physical layout of the database

*The Entity-relationship Model

- Models an enterprise as a collection of entities and relationships

entity : a thing or object in the enterpries that is distinguishable from other objects

relationship : an association among several entities

*Object-relational Data Model

-Extend the relational data model by including object orientation and constructs to deal with added data   types

1.7 Storage Management

-a program module that provies the interface between the low-level data stored in the database and the   application programs and queries submitted to the system

1.8 Query Processing

1. Parsing and translation
2. Optimization
3. Evaluation이 이상은 이해가 안됬습니다.

1.9 Transaction Management

Transaction : a collection of operations that perfoms a single logical function in database application

1.10 Database Architecture

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