Introduction to Modern Database Systems PDF

Bicol University College of Science Computer Science and Information Technology Department Chapter 1 Introduction to Modern Database Systems CS105 - Information Management 1 Objectives In this chapter, you will learn:  The difference between data and information  What a database is, the vari...

Bicol University College of Science Computer Science and Information Technology Department Chapter 1 Introduction to Modern Database Systems CS105 - Information Management 1 Objectives In this chapter, you will learn:  The difference between data and information  What a database is, the various types of databases, and why they are valuable assets for decision making  The importance of database design  How modern databases evolved from file systems 2 Chapter 1 – Overview of Database Objectives (cont’d.)  About flaws in file system data management  The main components of the database system  The main functions of a database management 3 Chapter 1 – Overview of Database Importance of Databases  All businesses have to keep different kinds of data for decision making.  Purpose of all business information systems is to help businesses use information as an organizational resource.  Databases are specialized structures that allow computer-based systems to store, manage, and retrieve data  A good understanding of how these structures are created and their proper use is vital for any information systems professional 4 Chapter 1 – Overview of Database Why Databases? Databases solve many of the problems encountered in data management ○Used in almost all modern settings involving data management: Business Research Administration Important to understand how databases work and interact with other applications 5 Chapter 1 – Overview of Database Data vs. Information Data are raw facts Information is the result of processing raw data to reveal meaning Information requires context to reveal meaning Raw data must be formatted for storage, processing, and presentation Data are the foundation of information, which is the bedrock of knowledge 6 Chapter 1 – Overview of Database Data vs. Information (cont’d.) Data: building blocks of information Information produced by processing data Information used to reveal meaning in data Accurate, relevant, timely information is the key to good decision making Good decision making is the key to organizational survival Data management: focuses on proper generation, storage, and retrieval of data 7 Chapter 1 – Overview of Database Introducing the Database Database: shared, integrated computer structure that stores a collection of: ○End-user data: raw facts of interest to end user ○Metadata: data about data Provides description of data characteristics and relationships in data Complements and expands value of data Database management system (DBMS): collection of programs ○Manages structure and controls access to data 8 Chapter 1 – Overview of Database File-Based System Information is stored in permanent files. New applications are added to the system as the need arises. A company system has a number of application programs; each of them is designed to manipulate Figure 1.1. Example of a file-based system used by banks to manage data. data files. 9 Chapter 1 – Overview of Database Computerized File Systems A simple example of a customer data file for a small insurance company is shown in Figure 1.2. Figure 1. 2 Contents of a CUSTOMER File 10 Chapter 1 – Overview of Database  11 Chapter 1 – Overview of Database Basic File Terminology  Data – raw facts such as a telephone number, a birth name, a customer name, and a year-to-date (YTD) sales value. Data will have little meaning unless they have been organized in some logical manner.  Field – a character or group of characters (alphabetic or numeric) that has a specific meaning. A field is used to define and store data.  Record – A logically connected set of one or more fields that describes a person, place, or thing For example, the fields that constitute a customer record might consist of the customer’s name, address, phone number, date of birth, credit limit and unpaid balance.  File – a collection of related records. For example, a 12 Chapter 1 – Overview of Database file might contain data about the students currently Drawbacks of File System  Data redundancy: Data redundancy refers to the duplication of data. It often leads to higher storage costs and poor access time.  Data inconsistency: Data redundancy leads to data inconsistency when more than one record is stored, but fails to update all.  Data Isolation: Because data are scattered in various files, and files may be in different formats, writing new application programs to retrieve the appropriate data is difficult. 13 Chapter 1 – Overview of Database Drawbacks of File System (cont’d)  Dependency on application programs: Changing files would lead to change in application programs.  Atomicity issues: Atomicity of a transaction refers to “All or nothing”, which means either all the operations in a transaction executes or none.  Data Security: Data should be secured from unauthorized access, for example a student in a college should not be able to see the payroll details of the teachers, such kind of security constraints are difficult to apply in file processing systems. 14 Chapter 1 – Overview of Database Structural and Data Dependence Structural dependence: access to a file is dependent on its own structure ○All file system programs must be modified to conform to a new file structure Structural independence: change file structure without affecting data access Data dependence: data access changes when data storage characteristics change Data independence: data storage characteristics do not affect data access 15 Chapter 1 – Overview of Database Structural and Data Dependence (cont'd.) Files systems are both exhibit structural dependence and data dependence. Each program accessing the file must contain: ○Lines specifying opening of specific file type ○Record specification ○Field definitions 16 Chapter 1 – Overview of Database Data Redundancy File system structure makes it difficult to combine data from multiple sources ○Vulnerable to security breaches Organizational structure promotes storage of same data in different locations ○Islands of information Data stored in different locations is unlikely to be updated consistently Data redundancy: same data stored unnecessarily in different places 17 Chapter 1 – Overview of Database Data Redundancy (cont'd.) Data inconsistency: different and conflicting versions of same data occur at different places Data anomalies: abnormalities when all changes in redundant data are not made correctly ○Update anomalies: An agent has a new phone number, it must be changed in all records of that agent ○Insertion anomalies: A new agent would have to be entered with a dummy customer ○Deletion anomalies: Deleting a customer may delete the only record of an agent 18 Chapter 1 – Overview of Database Computerized File Systems A simple example of a customer data file for a small insurance company is shown in Figure 1.2. Figure 1. 2 Contents of a CUSTOMER File 19 Chapter 1 – Overview of Database Database A database is a shared, integrated computer structure that stores a collection of: ○End-user data, that is, raw facts of interest to the end user. ○Metadata, or data about data, through which the end-user data are integrated and managed. Database properties: ○representation of some aspect of the real world or a collection of data elements (facts)representing real-world information. ○logical, coherent and internally consistent. ○designed, built and populated with data for a specific purpose. ○Each data item is stored in a field. ○A combination of fields makes up a table. 20 Chapter 1 – Overview of Database Database Systems Database system consists of logically related data stored in a single logical data repository ○May be physically distributed among multiple storage facilities ○DBMS eliminates most of file system’s problems ○Current generation stores data structures, relationships between structures, and access paths Also defines, stores, and manages all access paths and components 21 Chapter 1 – Overview of Database Database Systems 22 Chapter 1 – Overview of Database The Database System Environment Database system: defines and regulates the collection, storage, management, use of data Five major parts of a database system: ○Hardware ○Software ○People ○Procedures ○Data 23 Chapter 1 – Overview of Database  24 Chapter 1 – Overview of Database The Database System Environment (cont'd.) Hardware: all the system’s physical devices Software: three types of software required ○Operating system software ○DBMS software ○Application programs and utility software 25 Chapter 1 – Overview of Database The Database System Environment (cont'd.) People: all users of the database system ○System and database administrators ○Database designers ○Systems analysts and programmers ○End users Procedures: instructions and rules that govern the design and use of the database system Data: the collection of facts stored in the database 26 Chapter 1 – Overview of Database The Database System Environment (cont'd.) Database systems are created and managed at different levels of complexity Database solutions must be cost- effective as well as tactically and strategically effective Database technology already in use affects selection of a database system 27 Chapter 1 – Overview of Database  28 Chapter 1 – Overview of Database Role and Advantages of the DBMS DBMS is a collection of programs that enables users to create and maintain databases and control all access to them DBMS is the intermediary between the user and the database ○Database structure stored as file collection ○Can only access files through the DBMS DBMS enables data to be shared DBMS integrates many users’ views of the data 29 Chapter 1 – Overview of Database  30 Chapter 1 – Overview of Database Role and Advantages of the DBMS (cont’d.) Advantages of a DBMS: ○Improved data sharing ○Improved data security ○Better data integration ○Minimized data inconsistency ○Improved data access ○Improved decision making ○Increased end-user productivity 31 Chapter 1 – Overview of Database Types of Databases Databases can be classified according to: ○Number of users ○Database location(s) ○Expected type and extent of use Single-user database supports only one user at a time ○Desktop database: single-user; runs on PC Multiuser database supports multiple users at the same time ○Workgroup and enterprise databases 32 Chapter 1 – Overview of Database Types of Databases (cont’d.) Centralized database: data located at a single site Distributed database: data distributed across several different sites Operational database: supports a company’s day-to-day operations ○Transactional or production database Data warehouse: stores data used for tactical or strategic decisions 33 Chapter 1 – Overview of Database Types of Databases (cont'd.) Unstructured data exist in their original state Structured data result from formatting ○Structure applied based on type of processing to be performed Semistructured data have been processed to some extent Extensible Markup Language (XML) represents data elements in textual format ○XML database supports semistructured XML data Chapter 1 – Overview of Database 34 Why Database Design Is Important Database design focuses on design of database structure used for end-user data ○Designer must identify database’s expected use Well-designed database: ○Facilitates data management ○Generates accurate and valuable information Poorly designed database: ○Causes difficult-to-trace errors 35 Chapter 1 – Overview of Database DBMS Functions DBMS performs several important functions that guarantee the integrity and consistency of the data in the database Data Dictionary Management ○DBMS stores definitions of the data elements and their relationships (metadata) in a data dictionary ○changes made in a database structure are automatically recorded in the data dictionary ○DBMS provides data abstraction, and it removes structural and data dependence from the system 36 Chapter 1 – Overview of Database DBMS Functions (cont'd.) Data storage management ○DBMS creates and manages complex structures required for data storage ○Also stores related data entry forms, screen definitions, report definitions, etc. ○Performance tuning: activities that make the database perform more efficiently ○DBMS stores the database in multiple physical data files 37 Chapter 1 – Overview of Database  38 Chapter 1 – Overview of Database DBMS Functions (cont'd.) Data transformation and presentation ○DBMS transforms data entered to conform to required data structures ○DBMS transforms physically retrieved data to conform to user’s logical expectations Security management ○DBMS creates a security system that enforces user security and data privacy ○Security rules determine which users can access the database, which items can be accessed, etc. 39 Chapter 1 – Overview of Database DBMS Functions (cont'd.) Multiuser access control ○DBMS uses sophisticated algorithms to ensure concurrent access does not affect integrity Backup and recovery management ○DBMS provides backup and data recovery to ensure data safety and integrity ○Recovery management deals with recovery of database after a failure Critical to preserving database’s integrity 40 Chapter 1 – Overview of Database DBMS Functions (cont'd.) Data integrity management ○DBMS promotes and enforces integrity rules Minimizes redundancy Maximizes consistency ○Data relationships stored in data dictionary used to enforce data integrity ○Integrity is especially important in transaction- oriented database systems 41 Chapter 1 – Overview of Database DBMS Functions (cont'd.) Database access languages and application programming interfaces ○DBMS provides access through a query language ○Query language is a nonprocedural language ○Structured Query Language (SQL) is the de facto query language Standard supported by majority of DBMS vendors 42 Chapter 1 – Overview of Database DBMS Functions (cont'd.) Database communication interfaces ○Current DBMSs accept end-user requests via multiple different network environments ○Communications accomplished in several ways: End users generate answers to queries by filling in screen forms through Web browser DBMS automatically publishes predefined reports on a Web site DBMS connects to third-party systems to distribute information via e-mail 43 Chapter 1 – Overview of Database Lack of Design and Data-Modeling Skills Most users lack the skill to properly design databases ○Despite multiple personal productivity tools being available Data-modeling skills ○Vital in the data design process Good data modeling facilitates communication between the designer, user, and the developer 44 Chapter 1 – Overview of Database The Database Developme nt Process 45 Chapter 1 – Overview of Database Database Systems and Other Organizational Information Management Systems Transaction processing systems - the lifeblood systems of the organization because they support the processing of "production" data— ○ for example, for inventory maintenance, accounts receivable and payable, and other accounting functions. Management information systems -used primarily by middle management to control the organization. ○ These systems derive much of their information by summarizing and abstracting data from transaction processing systems. ○ report oriented; standard reports are produced periodically (weekly, monthly, or annually) Decision support systems are designed to provide information for managerial decision making ○ often use mathematical and statistical techniques to manipulate and analyze data 46 Chapter 1 – Overview of Database DBMS Applications Telecom Industry Banking System Sales Airlines Education Online Shopping 47 Chapter 1 – Overview of Database Preparing for Your Database Professional Career 48 Chapter 1 – Overview of Database Summary Data are raw facts Information is the result of processing data to reveal its meaning Accurate, relevant, and timely information is the key to good decision making Data are usually stored in a database DBMS implements a database and manages its contents 49 Chapter 1 – Overview of Database Summary (cont'd.) Metadata is data about data Database design defines the database structure ○Well-designed database facilitates data management and generates valuable information ○Poorly designed database leads to bad decision making and organizational failure Databases evolved from manual and computerized file systems 50 Chapter 1 – Overview of Database Summary (cont'd.) In a file system, data stored in independent files ○Each requires its own management program Some limitations of file system data management: ○Requires extensive programming ○System administration is complex and difficult ○Changing existing structures is difficult ○Security features are likely inadequate ○Independent files tend to contain redundant data Structural and data dependency problems 51 Chapter 1 – Overview of Database Summary (cont'd.) Database management systems were developed to address file system’s inherent weaknesses DBMS present database to end user as single repository ○Promotes data sharing ○Eliminates islands of information DBMS enforces data integrity, eliminates redundancy, and promotes security 52 Chapter 1 – Overview of Database References Coronel, C. , Morris, S. and Rob, P. (2016) Database Systems: Design, Implementation and Management Hoffer, A. ,Ramesh V. and Topi, H. (2016) Modern Database Management 12th Edition: Design, Implementation and Management Watt, A. and N. Eng. (2014). Database Design – 2nd Edition. Victoria, B.C. Retrieved from https://opentextbc.ca/dbdesign01/. Singh, Chaitanya. DBMS Tutorial – Database Management Systems Tools https://beginnersbook.com/2015/04/dbms-tutorial/ 53 Chapter 1 – Overview of Database Thank you