17-05-2012, 12:22 PM
Entity Relationship in Airline Reservation System
air.pdf (Size: 67.35 KB / Downloads: 293)
INTRODUCTION
Over the course of last four decades of twentieth century, use
of databases grew in all enterprises. The internet revolution of
the late 1990s sharply increased direct user access to databases.
Organisations converted many of their phone interfaces to
databases into web interfaces, and made a variety of services
online. Therefore, it is very easy to book tickets and find other
information online related to airlines online.
IMPLEMENTATION
The overall logical structure (schema) of a database can be
expressed graphically by an Entity-Relationship diagram(E-R
diagram) . An E-R diagram can express the overall logical
structure of a database graphically. They are simple and clearqualities
that may well account in large part for the
widespread use of the E-R model. Such a diagram consists of
the following major components:
Rectangles, which represent entity sets, Ellipses which
represent attributes. Diamonds which represent relationship
sets. Lines which link attributes to entity sets and entity sets to
relationship sets. Double ellipses which represent multi valued
attributes. Dashed ellipses which denote derived attributes.
Double lines which indicate total participation of an entity in a
relationship set. Double rectangles which represent weak
entity sets.
APPLICATION
This kind of database is widely used in Airline Reservation
System where all the information related to. Flights,
reservations, customers can be kept without the fear of losing
it as Database Management Systems provide the facility of
Security and Recovery.
CONCLUSION
With the help of Entity-Relationship diagram we can create
the required database and perform queries. For example in
case of Airline Reservation System we can make queries like
to find the schedule time of a flight, number of booked seats
in a flight, flight fares etc with the help of query language like
SQL Relational Algebra, Relational Calculus etc. We can
represent a database that conforms to an E-R database schema
by a collection of tables. For each entity set and for each
relationship set in database, there is a unique table to which
we can assign the name of the corresponding entity set and
relationship set. Each table has multiple columns, each of
which has a unique name. Both the E-R model and the
relational-database model are abstract, logical representations
of real-world enterprises.