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Introduction to Database Systems

Introduction to Database Systems. Learning Objectives. Role of Databases Database Definition DBMS and its functions Kinds of DBMS’s Relational databases Actors in the database Environment Steps for designing a database A case study: A UNIVERSITY database. Role of Databases.

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Introduction to Database Systems

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  1. Introduction to Database Systems

  2. Learning Objectives • Role of Databases • Database Definition • DBMS and its functions • Kinds of DBMS’s • Relational databases • Actors in the database Environment • Steps for designing a database • A case study: A UNIVERSITY database

  3. Role of Databases Banks (amount deposit/ withdraw) Reservation Systems (hotel/ airline) Library Catalogs E-shopping Inventory Note: Database is not a static entity, Data stored require regular update.

  4. Database Definition A database is a collection of related data. A shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization

  5. How databases are created? • Databases may be created and maintained manually or it may be computerized. • Two ways to create and maintain a database: • A group of application programs are written specifically for that task. • Database management system (DBMS)

  6. DBMS: Database Management System • DBMS is a collection of programs that enables users to create and maintain a database. • The DBMS is a general-purpose software system that facilitates the processes of: • Defining • Constructing • Manipulating • Sharing Databases among various users and applications.

  7. Defining a Database • Defining a database involves specifying: • The data types • Structures • Constraints of the data to be stored in the database. • A database is defined using Data Definition language (DDL) • The database definition or descriptive information is also stored in the database in the form of a database catalog or dictionary; called data dictionary, meta data or data about data.

  8. Constructing a Database It is the process of storing the data on some storage medium that is controlled by the DBMS.

  9. Manipulating a Database • It includes functions as • querying the database to retrieve specific data, • updating (delete/ insert/ update) the database to reflect changes, • and generating reports from the data. • To manipulate a database DBMS uses Data Manipulation Language (DML).

  10. Sharing a Database Sharing a database allows multiple users and programs to access the database simultaneously.

  11. Other functions of DBMS • Protecting a database • System protection • Against hardware or software malfunction • Security protection • Against unauthorized or malicious access • Maintaining over a long period of time

  12. So What is a Database System? The database and DBMS software together form a database system.

  13. Kinds of DBMS’s Hierarchical databases Network databases Relational databases Object Oriented databases

  14. Relational Databases Bases on the concept of mathematical relations Data and relationships are represented as tables. Each relation has a unique name A relation has a number of columns with a unique name called attributes. A tupleis a row of a relation, also called as record. Each relation has a unique attribute that differs tuples from each other called as primary key. When the primary key becomes part of another relation it is called as foreign key.

  15. Steps for designing a database • Requirement definition and analysis • it involves the collection and analysis of the requirements of users and application areas. • Conceptual Design • The requirements are transformed into a conceptual design that can be represented and manipulated using some computerized tools so that it can be easily maintained, modified and transformed into a database implementation. • A model called Entity Relationship Model (ERM) is used for this purpose.

  16. Continued… • Logical Design • The conceptual design is then translated into logical design that can be expressed in a data model implemented in a commercial DBMS. • E.g. relational data model (A very popular one) • Physical design • The final stage is the physical design in which further specifications are provided for storing and accessing the database. • The database design is implemented, populated with actual data and continuously maintained to reflect the state of the database.

  17. Actors in the Database Environment • Data Administrator • Database Administrator • Database Designers • Application Programmers • End Users • Naïve • Sophisticated

  18. Data Administrator Responsible for the management of data resources such as: Database Planning Development and Maintenance of Standards Policies and Procedures Conceptual/ logical database design The DA consults with and advises senior managers ensuring that the direction of database development will ultimately support corporate objectives.

  19. Database Administrator Responsible for the physical realization of the database such as: Physical database design and implementation Security and integrity control Maintenance for the operational system Ensuring satisfactory performance for the applications and users. The role of the DBA is more technically oriented than DA.

  20. Logical Database Designer • Logical database designer is concerned with: • Identifying the data • Entities and attributes • Relationships between the data • Constraints on the data that is to be stored in the database. • The logical database designer must have a thorough and complete understanding of the organization’s data and its business rules. • Business rules describe the main characteristics of data as viewed by the organization. • “a student cannot have more than six courses in a semester”

  21. Physical Database Designer The physical database designer takes the logical data model and decides how it is to be physically realized. Mapping logical data model into a set of tables and integrity constraints. Selecting specific storage structures and access methods for the data to achieve good performance for the database activities. Designing any security measures required on the data.

  22. Application Programmers Once the database has been implemented, the application programs that provide the required functionality for the end-users must be implemented. This is done by Application programmer. It includes: Retrieving data Inserting Updating deleting

  23. End Users End users are clients for the database. Naïve users are typically unaware of the DBMS. Sophisticated users are familiar with the structure of the database and facilities provided by it.

  24. Case Study: UNIVERSITY DATABASE This database maintains information concerning students, courses and grades in a university environment. Table1: STUDENT

  25. Table 2: COURSE

  26. Table 3: GRADE REPORT

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