Database Design Introduction Ravi Kiran Kumar Meduri Lecturer

Database Design Introduction Ravi Kiran Kumar Meduri Lecturer in Computer Science Government Degree College Gummalakshmipuram Vizianagaram District

Agenda q Database design – an introduction q Database design steps q Conceptual design using ER modelling

Database – A quick recap q Data – A collection of known facts. q Database – A collection of related data. q Database Management System – A software system to define, construct, manipulate and share databases among various users and applications. q Data model – A collection of concepts that describe data types, relationships and constraints that apply to the data

Overview of Design Process q Essentially divided into two major parts: § Database design § Application programs design q Application programs focus on programs and interfaces that access database and is part of Software Engineering q Design of database is a collection processes that design, develop, implement and maintain enterprise data

Database Design – Why is it Needed? q Enterprise applications consist of a wide gamut of data operated by different users q Design is needed for: § Meeting users’ data requirements § Providing high performance § Improving data consistency § Reducing disk space § Enabling easier maintenance q Design is the gist of database management

Database Design – Definition of Schema q Schema – the description of a database q Schema defines the record structure, types of data items, constraints on data, etc. q Actual data is stored in the schema of the database. q Actual data changes frequently while the schema is not expected to change. q Schema is succinctly specified using a diagram called schema diagram and does not contain all the details of the schema

Three Schema Architecture q Objectives of database approach: § Catalog to store the database description § Data independence § Support of multiple user views q Solution – use a three schema architecture q Internal schema – physical storage structure q Conceptual schema – data types, relationships, constraints and operations of whole database q External schema – part of the database for a group of users

Data Independence q Physical data independence – it is the capacity to change the internal schema without having to change the conceptual schema q Logical data independence – it is the capacity to change the conceptual schema without having to change the external schema q Most DBMSs support physical data independence q Logical data independence is hard to achieve

Architecture to Design q Three schema architecture provides the basis for database design q Database design mainly focusses on producing § Conceptual design § Logical design § Physical design

Next Session? What are various steps involved in database design? How do we perform these activities?