8/3/2019 Relational Data Base Management System
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Basic concept of
RDBMS(Relational Data BaseManagement System)
The simplest model for a database is a flat file. You have only
a single table which includes
fields for each element you need to store. Nearly everyone has
worked with flat file databases.
The problem with flat files is that they
Waste storage space
Problematic to maintain
Lets consider the classic example of a customer order entry
system. Assume that you're
managing the data for a company with a number of customers, each
of which will be placing
multiple orders. In addition, each order can have one or more
items.
Before moving on, lets describe the data that we wish to record
for each component of theapplication:
Customers :Customer Number ,Company Name ,Address City, State
,Phone Number
Orders : Order Number, Order Date
Order Line Items: Item Number ,Description ,Quantity ,Price
It except some of the problems. Each time an order is placed,
you'll need to repeat the customer
information, including the Customer Number, Company Name, etc.
What's worse is that for each
item, you not only need to repeat the order information such as
the Order Number and OrderDate, but you also need to continue
repeating the customer information as well.
Example:- Lets say there's one customer who has placed two
orders, each with four line
items. To maintain this tiny amount of information, you need to
enter the Customer Number andCompany Name eight times.
If the company should send you a change of address, the number
of records you need to update is
equal to the sum of product of orders and order line items.
Obviously this will quickly become
unacceptable in terms of both the effort required to maintain
the data and the likelihood that atsome point there will be data
entry errors and the customer address will be inconsistent
between
records.
The solution to this problem is to use a Relational Data Base
model for the data. TheRelational Database is a collection of
tables. The use of relational database may use this tables
for inserting deleting and Modifying tables.The concept isn't
that hard to understand. It simply
means that in this example each order entered is related to a
customer record, and each line item
