ch1. introduction

◆ DBMS (database management system)

- collection of interrelated data

- set of programs to access to data

- environment both convenient and efficient to use

◆ drawbacks of using file systems to store data
- data redundancy and inconsistency (데이터 중복, 불일치)

- difficult in accessing data (데이터에 접근이 어려움)

- data isolation (데이터 고립)

- integrity problems (무결점성 문제)

- atomicity of updates (업데이트의 원자성)

- concurrent access by multiple users (동시 다중접근 문제)

- security problems (보안문제)

=>DBMS 는 위의 문제들을 해결할 수 있음.

◆ level of abstraction

- physical level : how a record is stored

- logical level : data stored in databases, and  the relationships among the data.

- view level : app programs hide details of data type. hide information for security

◆ view of data :  특정 목적으로 여러 개의  view  생성 가능

 

◆ instances and schemas

- schema : the logical structure of the database

- analogous to type information of a variable in a program

- physical schema , logical schema

- instance : the actual content of the database at a particular point in time

- analogous to the value of a variable

- physical data independence : the ability to modify the physical schema without changing the logical schema ( 사용자는 logical level만!!! )

- applications depend on the logical schema

 

◆ data models

- modeling elements : data / data relationship / data semantics / data constraints

  => collection of tools for describing above.

- Relational model

- Entity-relationship data model

- Object-based data models

- Semistructured data model

- Other older models ..

 

◆ data manipulation language (DML)

- also known as query language

- 2 classes 

> procedural : 사용자가 어떤 데이터가 필요하며, 데이터를 어떻게 얻어 올 것인지 명시
  [ 절차적 ]

> declarative (non-procedural) : 사용자는 어떤 데이터가 필요한지만 명시하면 됨

  [ 비절차적 ] 

- SQL ~ declarative

◆ data definition language (DDL)

- specification notation for defining the database schema

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

  (참고) data dictionary -  테이블 생성시기, 권한, 통계정보 등 다양한 정보를 갖고 있음

- Data dictionary contains metadata (즉, data about data)

- database schema

- integrity constraints 

- primary key ( uniquely identify )

- referential integrity

- authorization 

◆ relational model

 

◆ SQL : widely used non-procedural language (declarative)

 

◆ database design

- logical design - deciding on the database schema. 

- physical design - deciding on the physical layout of the database

 

- 설계 잘못하면 ~ 정보의 중복이 많음. 의도치 않게 정보를 삭제하는 경우가 발생할 수있음

 

◆ design approaches

- normal theory 

- E-R model

 

◆ storage management

- storage manager : program module that provides the interface between the low-level data stored in the database and the application programs and queries submitted to the system.

- storage manager 

~ interaction wit/ the file manager

~ efficient storing, retrieving and updating of data

- issue : storage access / file organization / indexing and hashing

 

◆ query processing

 

◆ transaction management 

- transaction : collection of operations that performs a single logical function in a database application

- transaction management component

- concurrency-control manager (for multi-user)

- transaction ~ atomicity!(all or nothing) / ~ recovery

◆ data mining and analysis : to find useful patterns and rules

 

◆ database architecture

- centralize / client-server / parallel(병렬, 위치고려안함) / distributed (분산,위치따로)

 

◆ database users : users are differentiated by the way they expect to interact with the system

- application programmers

- sophisticated users

- specialized users

- naive users

 

◆ database administrator //pass

- coordinates all the activities of the database system

- database administrator's duties...

 

◆ history of database systems