Chapter 1 Database Systems

11eDatabase SystemsDesign, Implementation, and ManagementCoronel MorrisChapter 1Database Systems 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.

Learning Objectives In this chapter, you will learn: The difference between data and information What a database is, the various types of databases, andwhy they are valuable assets for decision making The importance of database design How modern databases evolved from file systems 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.2

Learning Objectives In this chapter, you will learn: About flaws in file system data management The main components of the database system The main functions of a database management system(DBMS) 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.3

Data vs. InformationData Raw facts Raw data - Not yet beenprocessed to reveal themeaning Building blocks of information Data managementInformation Produced by processing data Reveals the meaning of data Enables knowledge creation Should be accurate, relevant, andtimely to enable good decisionmaking Generation, storage, andretrieval of data 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.4

Database Shared, integrated computer structure that stores acollection of: End-user data - Raw facts of interest to end user Metadata: Data about data, which the end-user data areintegrated and managed Describe data characteristics and relationships Database management system (DBMS) Collection of programs Manages the database structure Controls access to data stored in the database 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.5

Role of the DBMS Intermediary between the user and the database Enables data to be shared Presents the end user with an integrated view of thedata Receives and translates application requests intooperations required to fulfill the requests Hides database’s internal complexity from theapplication programs and users 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.6

Figure 1.2 - The DBMS Manages the Interactionbetween the End User and the Database 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.7

Advantages of the DBMS Better data integration and less data inconsistency– Data inconsistency: Different versions of the same dataappear in different places Increased end-user productivity Improved: Data sharing Data security Data access Decision making Data quality: Promoting accuracy, validity, andtimeliness of data 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.8

Types of Databases Single-user database: Supports one user at a time Desktop database: Runs on PC Multiuser database: Supports multiple users at thesame time Workgroup databases: Supports a small number ofusers or a specific department Enterprise database: Supports many users acrossmany departments 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.9

Types of Databases Centralized database: Data is located at a singlesite Distributed database: Data is distributed acrossdifferent sites Cloud database: Created and maintained usingcloud data services that provide definedperformance measures for the database 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.10

Types of Databases General-purpose databases: Contains a widevariety of data used in multiple disciplines Discipline-specific databases: Contains datafocused on specific subject areas 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.11

Types of Databases Operational database: Designed to support acompany’s day-to-day operations Analytical database: Stores historical data andbusiness metrics used exclusively for tactical orstrategic decision making Data warehouse: Stores data in a format optimized fordecision support 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.12

Types of Databases Online analytical processing (OLAP) Enable retrieving, processing, and modeling data from thedata warehouse Business intelligence: Captures and processes businessdata to generate information that support decisionmaking 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.13

Types of Databases Unstructured data: It exists in their original state Structured data: It results from formatting Structure is applied based on type of processing to beperformed Semistructured data: Processed to some extent Extensible Markup Language (XML) Represents data elements in textual format 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.14

Database Design Focuses on the design of the database structure thatwill be used to store and manage end-user data Well-designed database Facilitates data management Generates accurate and valuable information Poorly designed database causes difficult-to-traceerrors 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.15

Evolution of File System Data ProcessingManual File SystemsAccomplished through a system of file folders and filing cabinetsComputerized File SystemsData processing (DP) specialist: Created a computer-based system that would track dataand produce required reportsFile System Redux: Modern End-User Productivity ToolsIncludes spreadsheet programs such as Microsoft Excel 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.16

Table 1.2 - Basic File Terminology 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.17

Figure1.6 - A Simple File System 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.18

Problems with File System Data ProcessingLengthy development timesDifficulty of getting quick answersComplex system administrationLack of security and limited data sharingExtensive programming 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.19

Structural and Data Dependence Structural dependence: Access to a file is dependenton its own structure All file system programs are modified to conform to anew file structure Structural independence: File structure is changedwithout affecting the application’s ability to accessthe data 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.20

Structural and Data Dependence Data dependence Data access changes when data storage characteristicschange Data independence Data storage characteristics is changed withoutaffecting the program’s ability to access the data Practical significance of data dependence isdifference between logical and physical format 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.21

Data Redundancy Unnecessarily storing same data at different places Islands of information: Scattered data locations Increases the probability of having different versions ofthe same data 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.22

Data Redundancy Implications Poor data security Data inconsistency Increased likelihood of data-entry errors whencomplex entries are made in different files Data anomaly: Develops when not all of the requiredchanges in the redundant data are made successfully 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.23

Types of Data AnomalyUpdate AnomaliesInsertion AnomaliesDeletion Anomalies 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.24

Lack of Design and Data-Modeling Skills Evident despite the availability of multiple personalproductivity tools being available Data-modeling skills is vital in the data designprocess Good data modeling facilitates communicationbetween the designer, user, and the developer 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.25

Database Systems Logically related data stored in a single logical datarepository Physically distributed among multiple storage facilities DBMS eliminates most of file system’s problems Current generation DBMS software:– Stores data structures, relationships between structures, andaccess paths– Defines, stores, and manages all access paths andcomponents 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.26

Figure 1.8 - Contrasting Database and FileSystems 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.27

Figure 1.9 - The Database System Environment 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.28

DBMS FunctionsData dictionary management Data dictionary: Stores definitions of the data elements and their relationshipsData storage management Performance tuning: Ensures efficient performance of the database in terms ofstorage and access speedData transformation and presentation Transforms entered data to conform to required data structuresSecurity management Enforces user security and data privacy 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.29

DBMS FunctionsMultiuser access control Sophisticated algorithms ensure that multiple users can access thedatabase concurrently without compromising its integrityBackup and recovery management Enables recovery of the database after a failureData integrity management Minimizes redundancy and maximizes consistency 2015 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.30