Database system
- 1. Chapter 1 Introduction to Databases Transparencies
- 2. 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).
- 3. 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.
- 4. 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
- 5. 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.
- 7. Limitations of File-Based Approach • Separation and isolation of data o Each program maintains its own set of data. o Users of one program may be unaware of potentially useful data held by other programs. • Duplication of data o Same data is held by different programs. o Wasted space and potentially different values and/or different formats for the same item.
- 8. Limitations of File-Based Approach • Data dependence o File structure is defined in the program code. • Incompatible file formats o Programs are written in different languages, and so cannot easily access each other’s files. • Fixed Queries/Proliferation of application programs o Programs are written to satisfy particular functions. o Any new requirement needs a new program.
- 9. Database Approach • Arose because: o Definition of data was embedded in application programs, rather than being stored separately and independently. o No control over access and manipulation of data beyond that imposed by application programs. • Result: o the database and Database Management System (DBMS).
- 10. 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.
- 11. 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.
- 13. Database Approach • Data definition language (DDL). o Permits specification of data types, structures and any data constraints. o All specifications are stored in the database. • Data manipulation language (DML). o General enquiry facility (query language) of the data.
- 14. Database Approach • Controlled access to database may include: o a security system o an integrity system o a concurrency control system o a recovery control system o a user-accessible catalog.
- 15. Views • Allows each user to have his or her own view of the database. • A view is essentially some subset of the database.
- 16. 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
- 18. Components of DBMS Environment • Hardware o Can range from a PC to a network of computers. • Software o DBMS, operating system, network software (if necessary) and also the application programs. • Data o Used by the organization and a description of this data called the schema.
- 19. Components of DBMS Environment • Procedures o Instructions and rules that should be applied to the design and use of the database and DBMS. • People
- 20. Roles in the Database Environment • Data Administrator DA • Database Administrator (DBA) • Database Designers (Logical and Physical) • Application Programmers • End Users (naive and sophisticated)
- 21. History of Database Systems • First-generation o Hierarchical and Network • Second generation o Relational • Third generation o Object-Relational o Object-Oriented
- 22. 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
- 23. 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
- 24. Disadvantages of DBMSs • Complexity • Size • Cost of DBMS • Additional hardware costs • Cost of conversion • Performance • Higher impact of a failure