CMT 302 - Advanced Database Systems Lecture Notes PDF

CMT 302 – ADVANCED DATABASE SYSTEMS LEC 3 – LECTURE 1&2 BY NAME: PROF. BARASA JOEL EMAIL: [email protected] PHONE: +254769257365 0R +254705451853 Chapter 1 Introduction to Databases Transparencies © All rights r...

CMT 302 – ADVANCED DATABASE SYSTEMS LEC 3 – LECTURE 1&2 BY NAME: PROF. BARASA JOEL EMAIL: [email protected] PHONE: +254769257365 0R +254705451853 Chapter 1 Introduction to Databases Transparencies © All rights reserved by Prof. Joel Barasa Chapter 1 - Objectives Some common uses of database systems. Characteristics of file-based systems. Problems with file-based approach. Meaning of the term database. Meaning of the term Database Management System (DBMS). © All rights reserved by Prof. Joel Barasa Chapter 1 - Objectives Typical functions of a DBMS. Major components of the DBMS environment. Personnel involved in the DBMS environment. History of the development of DBMSs. Advantages and disadvantages of DBMSs. © All rights reserved by Prof. Joel Barasa 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 © All rights reserved by Prof. Joel Barasa File-Based Systems Collection of application programs that perform services for the end users (e.g. reports). Each program defines and manages its own data. © All rights reserved by Prof. Joel Barasa File-Based Processing © All rights reserved by Prof. Joel Barasa Limitations of File-Based Approach Separation and isolation of data – Each program maintains its own set of data. – Users of one program may be unaware of potentially useful data held by other programs. Duplication of data – Same data is held by different programs. – Wasted space and potentially different values and/or different formats for the same item. © All rights reserved by Prof. Joel Barasa Limitations of File-Based Approach Data dependence – File structure is defined in the program code. Incompatible file formats – Programs are written in different languages, and so cannot easily access each other’s files. Fixed Queries/Proliferation of application programs – Programs are written to satisfy particular functions. – Any new requirement needs a new program. © All rights reserved by Prof. Joel Barasa Database Approach Arose because: – Definition of data was embedded in application programs, rather than being stored separately and independently. – No control over access and manipulation of data beyond that imposed by application programs. Result: – the database and Database Management System (DBMS). © All rights reserved by Prof. Joel Barasa 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. © All rights reserved by Prof. Joel Barasa Database Management System (DBMS) A software system that enables users to define, create, maintain, and control access to the database. (Database) application program: a computer program that interacts with database by issuing an appropriate request (SQL statement) to the DBMS. © All rights reserved by Prof. Joel Barasa Database Management System (DBMS) © All rights reserved by Prof. Joel Barasa Database Approach Data definition language (DDL). – Permits specification of data types, structures and any data constraints. – All specifications are stored in the database. Data manipulation language (DML). – General enquiry facility (query language) of the data. © All rights reserved by Prof. Joel Barasa Database Approach Controlled access to database may include: – a security system – an integrity system – a concurrency control system – a recovery control system – a user-accessible catalog. © All rights reserved by Prof. Joel Barasa Views Allows each user to have his or her own view of the database. A view is essentially some subset of the database. © All rights reserved by Prof. Joel Barasa Views - Benefits Reduce complexity Provide a level of security Provide a mechanism to customize the appearance of the database Present a consistent, unchanging picture of the structure of the database, even if the underlying database is changed © All rights reserved by Prof. Joel Barasa Components of DBMS Environment © All rights reserved by Prof. Joel Barasa Components of DBMS Environment Hardware – Can range from a PC to a network of computers. Software – DBMS, operating system, network software (if necessary) and also the application programs. Data – Used by the organization and a description of this data called the schema. © All rights reserved by Prof. Joel Barasa Components of DBMS Environment Procedures – Instructions and rules that should be applied to the design and use of the database and DBMS. People © All rights reserved by Prof. Joel Barasa Roles in the Database Environment Data Administrator (DA) Database Administrator (DBA) Database Designers (Logical and Physical) Application Programmers End Users (naive and sophisticated) © All rights reserved by Prof. Joel Barasa History of Database Systems First-generation – Hierarchical and Network Second generation – Relational Third generation – Object-Relational – Object-Oriented © All rights reserved by Prof. Joel Barasa Advantages of DBMSs Control of data redundancy Data consistency More information from the same amount of data Sharing of data Improved data integrity Improved security Enforcement of standards Economy of scale © All rights reserved by Prof. Joel Barasa Advantages of DBMSs Balance conflicting requirements Improved data accessibility and responsiveness Increased productivity Improved maintenance through data independence Increased concurrency Improved backup and recovery services © All rights reserved by Prof. Joel Barasa Disadvantages of DBMSs Complexity Size Cost of DBMS Additional hardware costs Cost of conversion Performance Higher impact of a failure © All rights reserved by Prof. Joel Barasa END OF THE LECTURE