An Overview of Database Management

An Example A database system Database Tables, records, SQL Operations A computerized record-keeping system Database A repository for a collection of computerized data files A kind of electronic filing cabinet Tables, records, SQL Operations Add, insert, retrieve, update, delete, remove ※Repository: 저장소, operation: 연산

The wine cellar database

Retrieval 검색 SELECT WINE, BIN#, PRODUCER FROM CELLAR WHERE READY=2000; Cab.Sanvignon 43 Windsor Pinot Noir 51 Stemmler Merlot 58 Clos Du Bois

Insert, update, delete 삽입, 갱신, 삭제 INTO CELLAR(BIN#, WINE, PRODUCER, YEAR, BOTTLES, READY) VALUES(53, ‘Pinot Noir’, ‘Saintsbury’, 1997, 6, 2001) UPDATE CELLAR SET BOTTLES =4 WHERE BIN# = 3; DELETE FROM CELLAR WHERE BIN# = 2;

What is a database system? A computerized record-keeping system Components Data H/W S/W Users ※Record-keeping: 기록유지관리

Data in database system Integrated Unification of several distinct files Ex) student files, book files Shared Being shared among different users with different purposes Ex) book tables among students and librarians ※Integrated: 통합된, Shared: 공유된

H/W in database system Secondary storage devices – disk Processor(s) and main memory to support the execution of the database system S/W ※secondary storage device: 이차저장장치

S/W in database system DBMS(database management system) Also known as database manager Database server The shielding of database users from hardware-level details Ex) Microsoft ACCESS, Microsoft SQL Server, MySQL, ORACLE, DB2, SQLite… ※shield: 방패

Users in database system Application programmers Write database application programs in some programming language such as C, C++, Java, Visual Basic, COBOL, … End users Use the system online thru interface Interface Built-in query language processor Command-driven interfaces Menu- or forms-driven interfaces DBA (database administrator) Creates and maintains database

What is a database? Database A collection of shared persistent data used by the application systems of some particular enterprise Persistent data Data that live long time Differ from short-lived data like input data, output data, intermediate results---transient in nature ※intermediate: 중간의

Example A manufacturing company – product data A bank – account data A hospital – patient data A university – student data A government department – planning data

Entities and relationships 개체, 관계성 A medium to represent database for an enterprise conceptually. Entities Independent, distinguishable objects Relationship Unary Binary Ternary ※unary:일진, Binary:이진, ternary:삼진

Example of E/R A manufacturing company: KnowWare Inc. Wants to record data about The projects on hand The parts used in the projects The suppliers who supply the parts The warehouses in which those parts are stored The employees who work on the projects  entities

Example of E/R There are relationships linking entities - bidirectional SP (suppliers and parts) Each supplier supplies certain parts Each part is supplied by certain suppliers PJ (projects and parts) Parts are used in projects Projects use parts WP (warehouse and parts) Parts are stored in warehouses Warehouses store parts ※Bidirectional: 양방향의

Ex) SP relationship *given a supplier, get the parts supplied by that supplier *given a part, get the suppliers who supply that part Entity/relationship diagram (E/R diagram for short)

Properties Entities and relationships can be regarded as having properties corresponding to the data we wish to record about them Ex) suppliers: name, city, … ※property: 특성

Why database? Advantages over paper-based method of record keeping Compactness No need for voluminous paper files Speed Less drudgery Elimination of maintaining files by hand Currency Accurate, up-to-date information Centralized control in multi-user environment ※drudgery: 힘들고 반복적인 일, currency: 최신

Benefits of database Data sharing Reduction of redundancy Not only existing applications but also new applications Reduction of redundancy Integration by DBA Controlled redundancy Avoidance of inconsistency Corollary of reduction of redundancy ※Redundancy: 중복성, corollary: 계, 당연한 결론

Benefits of database Transaction support Transaction: a logical unit of work Ex) transfer of money from account A to B Account A and B have to be updated What if crash occurs before update of account B? ※crash: 시스템 고장

Benefits of database Integrity Security Data in the database is accurate Security Having the complete jurisdiction over the data by DBA Ensure proper channels to access DB Define security rules for sensitive data (read, write, modify) ※integrity: 무결성, jurisdiction: 관할권

Benefits of database Balancing conflicting requirements Standards Ex) Internal storage method of data For fast access for the most important applications : eg. Index structure slower access for certain other applications : eg. sequential file structure Standards Representation of data Aid to data interchange or migration between systems ※sequential file: 순차파일

Benefits of database Data independence Separation of physical and logical aspect of database DBA can change physical storage structure and access strategy without having to modify existing applications ※access-strategy: 액세스방법