Chapter 1 Database Systems PDF

Chapter 1 Database Systems ©2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain...

Chapter 1 Database Systems ©2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part, except for use as permitted in a license distributed with a certain product or service or otherwise on a password-protected website or school-approved learning management system for classroom use..  Learning Objectives Data vs information What a database is, the various types of databases The importance of database design How modern databases evolved from file systems The main components of the database system The main functions of a database management system (DBMS) 2 3  Data vs. Information Data Information Raw facts § Produced by processing raw Raw data - Not yet been data to reveal its meaning processed to reveal the § Enables knowledge creation meaning § Should be accurate, relevant, Building blocks of information and timely to enable good decision making 4 Introducing the Database Shared, integrated computer structure that stores a collection of: End-user data - Raw facts of interest to end user Metadata: Data about data, which the end-user data are integrated and managed - Describe data characteristics and relationships that links the data found within the database Database management system (DBMS) Collection of programs Manages the database structure Controls access to data stored in the database 5  DBMS 6 http://www.bbc.co.uk/education/guides/zb2hgk7/revision  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 the data Receives and translates application requests into operations required to fulfil the requests Hides database’s internal complexity from the application programs and users 7 Figure 1.3 - The DBMS Manages the Interaction between the End User and the Database 8  Advantages of the DBMS Better data integration and less data inconsistency Data inconsistency: Different versions of the same data appear in different places Increased end-user productivity Improved - Data sharing - Data security - Data access - Decision making Data quality: Accuracy, validity, and timeliness of data 9  Types of Databases Databases can be classified by: Number of Type of Intended Structured Data users stored data data location supported data usage degree 10 Types of Databases (cont..) Single-user database: Supports one user at a time Desktop database: Runs on PC Number Multi-user database: Supports of users multiple users at the same time supported Workgroup databases: Supports a small number of users or a specific department Enterprise database: Supports many users across many departments 11  Types of Databases (cont..) Centralized database: Data is located at a single site Distributed database: Data is distributed across different sites Data Cloud database: Created and maintained using cloud data services location that provide defined performance measures (data storage capacity, required throughput, availability) for the database 12  Types of Databases (cont..) General-purpose databases: Contains a wide variety of data used in multiple disciplines Type Eg: LexisNexis, ProQuest of Discipline-specific databases: stored Contains data focused on data specific subject areas – mainly used for research purpose e.g: CompuStat, GIS, medical 13 Types of Databases (cont..) Operational database: Designed to support a company’s day-to-day operations Analytical database: Stores historical data and business metrics used exclusively for tactical or strategic decision Data making usage Data warehouse: Stores data in a Business intelligence : format optimized for decision support Captures and Online analytical processing (OLAP) : processes Enable retrieving, processing, and business data to modeling data from the data warehouse generate information that support decision making 14  Types of Databases (cont..) Unstructured data: It exists in their original state Structured data: It results from formatting Structured data Structure is applied based on degree type of processing to be performed Extensible Semi-structured data: Markup Processed to some extent Language (XML) Represents data elements in textual format 15  Database design Focuses on the design of the database structure that will 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-trace errors 16 Why Database Design is Important? (cont…) 17 Why Database Design is Important? (cont…) Refer to Fig 1.5, pp. 13 18  Evolution of File System Data Processing Manual File Systems Accomplished through a system of file folders and filing cabinets Computerized File Systems Data processing (DP) specialist: Created a computer-based system that would track data and produce required reports File System Redux: Modern End-User Productivity Tools Includes spreadsheet programs such as Microsoft Excel enabled users to conduct sophisticated data analysis which helps them understanding data and make better decisions 19  Manual file systems Filing cabinet by mightymightymatze (CC BY-NC) ten boxes by Jenny Spadafora (CC BY-NC-SA) 20 Computerized File Systems 21 Table 1.2 - Basic File Terminology 22 Problems with File System Data Processing Lengthy development times Difficulty of getting quick answers Complex system administration Lack of security and limited data sharing Extensive programming 23  Problems with File System Data Processing (cont…) Structural Dependence Structural dependence: Access to a file is dependent on its own structure All file system programs are modified to conform to a new file structure Structural independence: File structure is changed without affecting the application’s ability to access the data 24  Problems with File System Data Processing (cont…) Data Dependence Data dependence Data access changes when data storage characteristics change Data independence Data storage characteristics is changed without affecting the program’s ability to access the data 25 Problems with File System Data Processing (cont…) Data Redundancy Unnecessarily storing same data at different places Islands of information: Scattered data locations Increases the probability of having different versions of the same data Data redundancy implications Poor data security Data inconsistency (lack data integrity) Increased likelihood of data-entry errors when complex entries are made in different files 26  Problems with File System Data Processing (cont…) Data Anomaly Data anomaly: Develops when not all of the required changes in the redundant data are made successfully Type of anomalies: Update anomalies- eg: Update Leah HP no Insertion anomalies - how to add new agent without customer? Deletion anomalies - eg: to delete customer, also delete agent. 27  Database Systems Logically related data stored in a single logical data repository Data repository appears to be a single unit to end user even though the data might be physically distributed among multiple storage facilities DBMS eliminates most of file system’s problems Current generation DBMS software: Stores data structures, relationships between structures, and access paths Defines, stores, and manages all access paths and components 28 Figure 1.8 - Contrasting Database and File Systems 29  The Database System Environment The database system is composed of five major parts : hardware, software, people, procedures and data 30  DBMS Functions Data dictionary Data dictionary: Stores definitions of management the data elements and their relationships Data storage management Performance tuning: Ensures efficient performance of the database in terms of storage and access speed Data transformation Transforms entered data to conform to and presentation required data structures 31  DBMS Functions Security management Enforces user security and data privacy Multiuser access Sophisticated algorithms ensure that multiple control users can access the database concurrently without compromising its integrity Backup and recovery Enables recovery of the database after a management failure 32  DBMS Functions Data integrity Minimizes redundancy and maximizes consistency management Database Query language: Lets the user specify what must be done without access having to specify how languages and application programming Structured Query Language (SQL): De facto query language and interfaces data access standard supported by the majority of DBMS vendors Database Accept end-user requests via multiple, different network communication environments interfaces 33 Disadvantages of Database Systems Increased costs Management complexity Maintaining currency Vendor dependence Frequent upgrade/replacement cycles 34