Chapter 1 Database Systems Database Systems: Design,

Chapter 1 Database Systems Database Systems: Design, Implementation, and Management, Sixth Edition, Rob and Coronel

In this chapter, you will learn: The difference between data and information What a database is, about different types of databases, and why they are valuable assets for decision making Why database design is important How modern databases evolved from files and file systems Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 2

In this chapter, you will learn: About flaws in file system data management How a database system differs from a file system, and how a DBMS functions within the database system Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 3

Data vs. Information Data: Raw facts; building blocks of information Unprocessed information Information: Data processed to reveal meaning Accurate, relevant, and timely information is key to good decision making Good decision making is key to survival in global environment Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 4

Sales per Employee for Each of ROBCOR’s Two Divisions Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 5

Introducing the Database and the DBMS Database—shared, integrated computer structure that houses: End user data (raw facts) Metadata (data about data) Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 6

Introducing the Database and the DBMS (continued) DBMS (database management system): Collection of programs that manages database structure and controls access to data Possible to share data among multiple applications or users Makes data management more efficient and effective Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 7

DBMS Makes Data Management More Efficient and Effective End users have better access to more and better-managed data Promotes integrated view of organization’s operations Probability of data inconsistency is greatly reduced Possible to produce quick answers to ad hoc queries Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 8

The DBMS Manages the Interaction Between the End User and the Database Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 9

Types of Databases Single-user: Supports only one user at a time Desktop: Single-user database running on a personal computer Multi-user: Supports multiple users at the same time Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 10

Types of Databases (continued) Workgroup: Multi-user database that supports a small group of users or a single department Enterprise: Multi-user database that supports a large group of users or an entire organization Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 11

Location of Databases Centralized: Supports data located at a single site Distributed: Supports data distributed across several sites Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 12

Uses of Databases Transactional (or production): Supports a company’s day-to-day operations Data warehouse: Stores data used to generate information required to make tactical or strategic decisions Such decisions typically require “data massaging” Often used to store historical data Structure is quite different Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 13

Why Database Design is Important Defines the database’s expected use Different approach needed for different types of databases Avoid redundant data (unnecessarily duplicated) Poorly designed database generates errors leads to bad decisions can lead to failure of organization Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 14

Brief History of Information Systems -1 Early human records-clay tablets, hieroglyphics, cave paintings, paper records of family histories, treaties, inventories, and so on Hollerith used punched cards in 1890 US census Punched paper tape introduced in 1940s Magnetic tape introduced about 1950-used in UNIVAC I Cards, paper tape, magnetic tape are sequential access devices Used in sequential processing applications such as payroll Batch processing uses master file and transaction file as input; produces new master file as output Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 15

Brief History of Information Systems Sequential Processing Payroll Master File Paycheck s and stubs Payroll Program Payroll report Transaction file with this week’s new payroll data New Payroll Master File Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 16

Brief History of Information Systems - 2 Magnetic disk introduced in 1950s - direct access device Programming languages COBOL and PL/1 developed in 1960s Early database models developed Hierarchical model IBM IMS developed for Apollo moon landing project IMS product released in 1968 Most popular pre-relational DBMS SABRE airline reservation system used IMS Network model GE IDS developed by Charles Bachman in early 1960s CODASYL DBTG proposed standards published in 1971 ANSI rejected proposal New standards published in 1973, 1978, 1981 and 1984 Provided standard terminology, notion of layered database architecture Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 17

Brief History of Information Systems-3 Relational model Proposed by E.F. Codd in 1970 paper, "A Relational Model of Data for Large Shared Data Banks" Strong theoretical foundation System R, late 1970s IBM’s prototype relational system Introduced SQL, Structured Query Language, now standard language Peterlee Relational Test Vehicle at IBM UK Scientific Laboratory INGRES at University of California, Berkeley ORACLE used some System R results Early microcomputer relational DBMSs :dBase, R:Base, Foxpro, Paradox Microsoft Access most popular microcomputer-based DBMS Oracle, DB2, Informix, Sybase, and Microsoft’s SQL Server most popular enterprise DBMSs Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 18

Brief History of Information Systems-4 Entity Relationship model P.P. Chen, 1976 Semantic model – tries to capture meaning Object-oriented model Can handle complex data Introduced in 1990s Object-relational model: object-oriented capabilities added to relational databases Data warehouses developed in 1990s Take data from many sources May store historical data Used for data mining, finding trends in data Internet provides access to vast network of databases E-commerce Wireless computing Thin clients such as PDAs Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 19

The Historical Roots of Database: Files and File Systems Although managing data through file systems is largely obsolete Understanding relatively simple characteristics of file systems makes complexity of database design easier to understand Awareness of problems that plagued file systems can help prevent similar problems in DBMS Knowledge of file systems is helpful if you plan to convert an obsolete file system to a DBMS Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 20

Manual File Systems Traditionally composed of collection of file folders kept in file cabinet Organization within folders was based on data’s expected use (ideally logically related) System was adequate for small amounts of data with few reporting requirements Finding and using data in growing collections of file folders became time-consuming and cumbersome Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 21

Conversion from Manual File System to Computer File System Could be technically complex, requiring hiring of data processing (DP) specialists DP specialists created file structures, wrote software, and designed application programs Resulted in numerous “home-grown” systems being created Initially, computer files were similar in design to manual files (see Figure 1.3) Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 22

Contents of Customer File Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 23

Basic File Terminology Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 24

Example of Early Database Design DP specialist wrote programs for reports: Monthly summaries of types and amounts of insurance sold by agents Monthly reports about which customers should be contacted for renewal Reports that analyzed ratios of insurance types sold by agent Customer contact letters summarizing coverage Additional reports were written as required Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 25

Example of Early Database Design (continued) Other departments requested databases be written for them SALES database created for sales department AGENT database created for personnel department Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 26

Contents of the Agent File Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 27

Evolution of Simple File System As number of databases increased, small file system evolved Each file used its own application programs Each file was owned by individual or department who commissioned its creation Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 28

A Simple File System Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 29

Example of Early Database Design (continued) As system grew, demand for DP’s programming skills grew Additional programmers hired DP specialist evolved into DP manager, supervising a DP department Primary activity of department (and DP manager) remained programming Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 30

Problems with File System Data Management Every task requires extensive programming in a third-generation language (3GL) Programmer must specify task and how it must be done Modern databases use fourth-generation language (4GL) Allows user to specify what must be done without specifying how it is to be done Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 31

Programming in 3GL Time-consuming, high-level activity Programmer must be familiar with physical file structure As system becomes complex, access paths become difficult to manage and tend to produce malfunctions Complex coding establishes precise location of files and system components and data characteristics Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 32

Programming in 3GL (continued) Ad hoc queries are impossible Writing programs to design new reports is time consuming As number of files increases, system administration becomes difficult Making changes in existing file structure is difficult File structure changes require modifications in all programs that use data in that file Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 33

Programming in 3GL (continued) Modifications are likely to produce errors, requiring additional time to “debug” the program Security features hard to program and therefore often omitted Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 34

Structural and Data Dependence Structural dependence Access to a file depends on its structure Data dependence Changes in database structure affect program’s ability to access data Logical data format How a human being views the data Physical data format How the computer “sees” the data Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 35

Field Definitions and Naming Conventions Flexible record definition anticipates reporting requirements by breaking up fields into their component parts Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 36

Sample Customer File Fields Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 37

Data Redundancy Data redundancy results in data inconsistency Different and conflicting versions of the same data appear in different places Errors more likely to occur when complex entries are made in several different files and recur frequently in one or more files Data anomalies develop when required changes in redundant data are not made successfully Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 38

Data Anomalies Modification anomalies Occur when changes must be made to existing records Insertion anomalies Occur when entering new records Deletion anomalies Occur when deleting records Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 39

Database vs. File System Problems inherent in file systems make using a database system desirable File system Many separate and unrelated files Database Logically related data stored in a single logical data repository Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 40

Contrasting Database and File Systems Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 41

The Database System Environment Database system is composed of 5 main parts: 1. 2. Hardware Software 3. 4. 5. Operating system software DBMS software Application programs and utility software People Procedures Data Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 42

The Database System Environment (continued) Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 43

DBMS Functions Performs functions that guarantee integrity and consistency of data Data dictionary management Data storage management defines data elements and their relationships stores data and related data entry forms, report definitions, etc. Data transformation and presentation translates logical requests into commands to physically locate and retrieve the requested data Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 44

DBMS Functions (continued) Security management Multi-user access control enforces user security and data privacy within database creates structures that allow multiple users to access the data Backup and recovery management provides backup and data recovery procedures Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 45

DBMS Functions (continued) Data integrity management Database access languages and application programming interfaces promotes and enforces integrity rules to eliminate data integrity problems provides data access through a query language Database communication interfaces allows database to accept end-user requests within a computer network environment Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 46

Illustrating Metadata with Microsoft Access Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 47

Illustrating Data Storage Management with Oracle Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 48

Summary Information is derived from data, which is stored in a database To implement and manage a database, use a DBMS Database design defines its structure Good design is important Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 49

Summary (continued) Databases were preceded by file systems Because file systems lack a DBMS, file management becomes difficult as a file system grows DBMS were developed to address file systems’ inherent weaknesses Database Systems: Design, Implementation & Management / Rob & Coronel Slide 1- 50