entry. Each table column represents a Field, which groups each piece or item of data among the records into specific categories or types of data. Eg. StuNo., StuName, StuAge, StuClass, StuSec.
A Table is known as a RELATION A Row is known as a TUPLE A column is known as an ATTRIBUTE 12th Computer Chapter - - Database Concepts StuNo StuName StuAge StuClass StuSec Kannan A Ramakrishnan A Vidhya B Britto A Padmaja B Attribute / Column Tuple / Row DataBase Structure Fig . Table / Relation Data Model . • A data model describes how the data can be represented and accessed from a software after complete implementation • It is a simple abstraction of complex real world data gathering environment. • The main purpose of data model is to give an idea as how the final system or software will look like after development is completed.
. . Types of Data Model Following are the different types of a Data Model • Hierarchical Model • Relational Model • Network Database Model • Entity Relationship Model • Object Model . Hierarchical Model Hierarchical model was developed by IBM as Information Management System.
In Hierarchical model, data is represented as a simple tree like structure form. This model represents a one-to-many relationship i.e parent-child relationship. One child can have only one parent but one parent can have many children. This model is mainly used in IBM Main Frame computers.
12th Computer Chapter - - Hierarchical Model Fig. . School Course Theory Lab Resources . Relational Model The Relational Database model was first proposed by E.F.
Codd in . Nowadays, it is the most widespread data model used for database applications around the world. The basic structure of data in relational model is tables (relations). All the information’s related to a particular type is stored in rows of that table.
Hence tables are also known as relations in a relational model. A relation key is an attribute which