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A model in database system mostly defines the organisation of data or structure and a set of operations on that data. Relational model is a easy model in which database is represented as a collection of "Relations", where every relation is represented by a two dimensional table. Therefore, because of its simplicity it is most commonly used. The following table shows a simple relation:
PERSON_ID
NAME
AGE
ADDRESS
1
Sanjay Prasad
35
b-4,Modi Nagar
2
Sharad Gupta
30
Pocket 2, Mayur
Vihar.
3
Vibhu Datt
36
c-2, New Delhi
Figure: A Sample Person Relation
Following are some of the benefits of relational model:
The easy tabular representation of database helps the user define and question the database conveniently. For example, you can simply find out the age of the person whose first name is "Vibhu".
As the database is a collection of tables, new data can be added and removed easily. Also, manipulation of data from several tables can be done simply using several basic operations. For instance, we can add a telephone number field in the table at Figure.
In relational databases the relational algebraic operations are used to influence database. These are mathematical operations and make sure accuracy (and less of ambiguity) as compared to other models.
One-way Associations When an association is traversed only in the one direction, then it is implemented as a pointer i.e.an attribute which contains an object reference. If mu
Question: AirwaysCentre, an international airline booking company currently uses a relational database system for their operations, which includes the following relations: P
How does a query tree represent a relational algebra expression? Ans: This includes transforming an initial expression (tree) into an equivalent expression (tree) that is
Question 1 Create a table student with attributes student name, roll number, total marks and percentage. Do the following operations Insert details in to the table Update
What is meant by object-oriented data model? The object-oriented paradigm is based on encapsulation of data and code related to an object in to a one unit, whose contents are n
Determine the Derived attribute to avoid re-computation Each class box consists of an ordered list of attributes and operations, each represented as a next string. We can find
What is property - properties of a database ? It is an integrated collection of logically related records. It consolidates separate files into a common pool of data records and
Consider the subsequent relations along with keys underlined Street (name, location, city) House (number, street_name) Lives (name, house_number) Define the above relations
WHAT IS DATABASE TECHNOLOGIES
Determine the advantage of object-orientation Finally, object-orientation has advantage of continuity throughout analysis, persistent representation and design implementation.
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