Database Systems - Chapter 1 PDF

Database Systems Chapter # 1 Databases and Database Users Chapter 1 1 Examples of Database Applications  Purchases from the supermarket  Purchases using your credit card  Booking a holiday at the travel agents  Using the local library  Taking out insurance ...

Database Systems Chapter # 1 Databases and Database Users Chapter 1 1 Examples of Database Applications  Purchases from the supermarket  Purchases using your credit card  Booking a holiday at the travel agents  Using the local library  Taking out insurance  Renting a video  Using the Internet  Studying at university Chapter 1 Definitions of Database  Def 1: Database is an organized collection of logically related data  Def 2: A database is a shared collection of logically related data that is stored to meet the requirements of different users of an organization  Def 3: A database is a self-describing collection of integrated records  Def 4: A database models a particular real world system in the computer in the form of data Chapter 1 Definitions  Data: stored representations of meaningful objects and events or  Referred to facts concerning objects and events that could be recorded and stored on computer media  Structured: numbers, text, dates  Unstructured: images, video, documents  Information: data processed to increase knowledge in the person using the data  Metadata: data that describes the properties and context of user data Chapter 1 4  What is a Database  Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.  System catalog (metadata) provides description of data to enable program–data independence.  Logically related data comprises entities, attributes, and relationships of an organization’s information. Chapter 1 5  Figure 1-1a Data in Context Context helps users understand data Chapter 1  Graphical displays turn data into useful information that managers can use for decision making and interpretation Chapter 1  Descriptions of the properties or characteristics of the data, including data types, field sizes, allowable values, and data context Chapter 1 The concept of a shared organizational database Management Marketing Product Planning Control Sales Development Corporate Database Accounting Manufacturing Accounts Accounts Scheduling Production Receivable Payable Chapter 1 9 A bit of History  Computer initially used for computational/ engineering purposes  Commercial applications introduced File Processing System Chapter 1 10  File Processing System  A collection of application programs that perform services for the end-users such as production of reports  Each program defines and manages its own data Chapter 1 11 File Processing Systems Library Examination Registration Library Examination Registration Applications Applications Applications Library Examination Registration Data Data Data Files Files Files Chapter 1 Program and Data Interdependence 12  File Processing Systems Library Examination Registration Reg_Number Reg_Number Reg_Number Name Name Name Father Name Address Father Name Books Issued Class Phone Fine Semester Address Grade Class Chapter 1 13 Files Based Processing Chapter 1 Disadvantages of File Processing  Program-Data Dependence  File structure is defined in the program code.  All programs maintain metadata for each file they use  Duplication of Data (Data Redundancy)  Different systems/programs have separate copies of the same data  Same data is held by different programs.  Wasted space and potentially different values and/or different formats for the same item.  Limited Data Sharing  No centralized control of data  Programs are written in different languages, and so cannot easily access each other’s files. Chapter 1 Disadvantages of File Processing  Lengthy Development Times  Programmers must design their own file formats  Excessive Program Maintenance  80% of of information systems budget  Vulnerable to Inconsistency  Change in one table need changes in corresponding tables as well otherwise data will be inconsistent Chapter 1 16 Problems with Data Redundancy  Waste of space to have duplicate data Chapter 1 SOLUTION: The DATABASE Approach  Central repository of shared data  Data is managed by a controlling agent  Stored in a standardized, convenient form This requires a Database and Database Management System (DBMS) Chapter 1  Advantages of Database Approach Library Examination Registration Library Examination Registration Applications Applications Applications Database Management System - Data Sharing - Data Independence - Controlled Redundancy University - Better Data Integrity Students Database Chapter 1 19 Database Management System  A software system that is used to create, maintain, and provide controlled access to users of a database  (Database) application program: A computer program that interacts with database by issuing an appropriate request (SQL statement) to the DBMS Chapter 1 Database Management System DBMS manages data resources like an operating system manages hardware resources Chapter 1 Chapter 1 Chapter 1