Introduction to Database Management Systems

Transcription

1 Introduction What is a? Why? Evolution of. File Systems Hierarchical Network Relational Next Generation Structure Introduction 1 What Is a? Real World Applications DB Software Hardware Application Tools Introduction 2 What Is a?... Hardware -- Computer equipments. Software --Effective, efficient, and reliable management for Data storage Data retrieval Data update -- insertion, modification, and deletion Automated tools -- DB design and application development -- Data collection Data -- Stored facts Information -- Extracted and derived data for specific purpose Introduction 3 Dave McDonald, GSU 1-1

2 What Is a?... Applications users Application programmers End Users administrators ( DBAs ) Manages the database Consult the users Develop and coordinate the DB application development Make database policies and data standard And more Introduction 4 Why? Real World Policies Goals, & Strategic Planning Operational Activities & Management Management Planning & Control Introduction 5 Corporate Strategic data Management data Operation data Benefits Centralized control of data Reduced data redundancy (reduced does not mean minimized) Reduced problems of inconsistency Promote data sharing Data Independence Improved application development The enforcement of Data standards Integrity requirements Security restrictions Introduction 6 Dave McDonald, GSU 1-2

3 Disadvantages Expensive software is not cheap Hardware required Higher operating costs Complexity...requires a Adminitrator (DBA) Programmers Recovery from failure is more difficult Greater susceptibility to sabotage Introduction 7 The Approach Is more than: simply acquiring a collecting and storing data in one integrated database hiring a DBA Is rooted in the attitude of: sharing valued data resources releasing control of these resources to a common responsible authority cooperating in the maintenance of those shared data resources Introduction 8 Evolution of Closing the gap Introduction 9 80's -- today Object-Oriented DB systems 80's Relational DB Systems 60's & 70's Hierarchical & Network Systems 50's File Systems Dave McDonald, GSU 1-3

4 File Systems (1950's) Basic constructs: A file contains a set of sequential data records Each record consists of a set of data fields Pointers linking records Indexing provides random access to the records. Basic operations Open, close, or reset a file, Read, write, or delete a record. ISAM ( Indexed Sequential Access Method ) VSAM ( Virtual Storage Access Method ) Introduction 10 Disadvantages of File Systems Uncontrolled data redundancy, data inconsistency Poor data sharing Difficult to keep up with changes Record format vs. user requirements Programs vs. record format Low productivity High maintenance cost Introduction 11 Hierarchical (1960's) course# title Prereq prereq# section# date time location teach emp# name take ID# name grade Introduction 12 Dave McDonald, GSU 1-4

5 Prereq Hierarchical c2 MW 4:40 RM e3 John e2 Sue e1 Fred 8140 sys Intro to 3310 Sys. Design... c1 MW 7:10 RM 232 c2 MW 7:10 RM 232 c1 MW 4:40 RM 200 s3 Peter A s1 Tom B s2 Lisa A s1 Tom A Introduction 13 Network (1970's) require course# title section# offer date time location teach emp# name take ID# name Introduction 14 Network... e1 Fred e2 Sue 3730 Intro. to c2 MW 4:40RM 200 c1 MW 7:10RM 232 c2 MW 7:10RM 232 s1 Tom s2 Lisa s3 Peter e3 John c1 MW 4:40RM 200 s4 Linda teach 3210 Intro. prog.... take Introduction 15 Dave McDonald, GSU 1-5

6 Disadvantages of these Complex record structures High maintenance cost Difficult to change Record structures and links Application programs Physical implementation dependent IMS is a hierarchical IDMS is a network. Introduction 16 Introduction 17 Relational (1980's) ID s1 s2 s3 s4 s5 Advantages: Simple representation Associative (declarative) queries -- User specifies what data are wanted and the figures out where and how to access the data Disadvantages: Name Jose Alice Tom Sue Steve Primitive data values Age Lower level representation Address Stone Mountain Buck Head Dunwoody Atlanta Stone Mountain DB2, ORACLE, INGRESS, etc. GPA Object-Oriented name, DOB GPA,... vote change-address take-course Is-adviced -by Professor name, rank, salary,... give-advice publish -articles get-promotion Group data and processes Introduction 18 Understand complex objects Easy to maintain and change Improved productivity ONTOS, GemStone, ObjectStore from Object Design, OpenODBetc. Dave McDonald, GSU 1-6

7 Structure Basic concepts Data independence DB Architecture Relational Algebra Data models Semantic Object -oriented Hierarchical Network OO Distributed Relational SQL Integrity rules Management Error Recovery Concurrency control Query optimization Design Methodology Design Introduction 19 E-R mapping Relation Normalization FD Update anomalies Normal forms No loss Decomposition Dave McDonald, GSU 1-7